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Cellular inhibitor of apoptosis protein-1 (cIAP-1) is member of inhibitor of apoptosis proteins (IAPs) which can affect apoptosis through interactions with caspases. cIAP-1 is a multi-domain protein and able to regulate apoptosis through interactions with proteins such as caspases and possesses E3 ligase activity. Human cIAP-1 contains three baculovirus IAP repeat (BIR) domains which are critical for protein–protein interactions. Here, we report NMR resonance assignments of the first BIR domain of human cIAP. Its secondary structures in solution were determined based on the assigned resonances. The dynamics of this domain was obtained, and our hydrogen–deuterium exchange experiment reveals that the first helix in BIR1 is exposed to the solvent. The availability of assignments of backbone and side chain resonances will be useful for probing protein–protein interactions. [ABSTRACT FROM AUTHOR]

Immunoglobulin E (IgE) plays a central role in allergic reactions. IgE is a dynamic molecule that is capable of undergoing large conformational changes. X-ray crystal structures of the Fc region of IgE in complex with various ligands have shown that IgE-Fc can exist in extended and various bent conformations. IgE-Fc consists of three domains: Cε2, Cε3 and Cε4. While the complete NMR backbone assignments of the Cε2 and Cε3 domains have been reported previously, the Cε4 domain has not been assigned. Here, we report the complete backbone assignment of the Cε4 homodimer. Cε4 can be used as a model system to study dynamics and allostery in IgE, as both molecules exist as homodimers and exhibit similar binding properties to a number of ligands. [ABSTRACT FROM AUTHOR]

Bacterial tRNA (guanine37-N1)-methyltransferase (TrmD) plays important roles in translation, making it an important target for the development of new antibacterial compounds. TrmD comprises two domains with the N-terminal domain binding to the S-adenosyl-l-methionine (SAM) cofactor and the C-terminal domain critical for tRNA binding. Bacterial TrmD is functional as a dimer. Here we report the backbone NMR resonance assignments for the full length TrmD protein of Pseudomonas aeruginosa. Most resonances were assigned and the secondary structure for each amino acid was determined according to the assigned backbone resonances. The availability of the assignment will be valuable for exploring molecular interactions of TrmD with ligands, inhibitors and tRNA. [ABSTRACT FROM AUTHOR]

BAF200 is a subunit of PBAF chromatin remodeling complex that contains an N-terminal AT-rich interaction domain (ARID). ARID domain in general has been shown to bind to the AT-rich DNA sequences. The human BAF200 ARID (~ 110 residues) has the potential to bind the DNA sequences with high affinity, however, the structure and the exact contribution of hBAF200 ARID in PBAF functions as well its DNA binding specificities have not been established. In this study, we have expressed and purified the hBAF200 ARID for NMR studies. We report the complete backbone 1H, 13C, and 15N chemical shift assignment and secondary structure of hBAF200 ARID domain. [ABSTRACT FROM AUTHOR]

Bacterial tRNA (guanine37-N1)-methyltransferase (TrmD) is an important antibacterial target due to its essential role in translation. TrmD has two domains connected with a flexible linker. The N-terminal domain (NTD) of TrmD contains the S-adenosyl-l-methionine (SAM) cofactor binding site and the C-terminal domain is critical for tRNA binding. Here we report the backbone NMR resonance assignments for NTD of Pseudomonas aeruginosa TrmD. Its secondary structure was determined based on the assigned resonances. Relaxation analysis revealed that NTD existed as dimers in solution. NTD also exhibited thermal stability in solution. Its interactions with SAM and other compounds suggest it can be used for evaluating SAM competitive inhibitors by NMR. [ABSTRACT FROM AUTHOR]

Repressor of primer (Rop, or ROM, RNA I modulator) is a 63 amino acid four-helix bundle protein that exists in solution as an anti-parallel homodimer. This protein has been extensively studied, including by X-ray crystallography, NMR, rational design, and combinatorial mutagenesis. Previous NMR experiments with wild-type Rop were carried out at pH 2.3 and pH 6.3. In this paper, we report complete N-H backbone assignments for three variants of Rop under the same pH 6.3 conditions: wild-type Rop; a cysteine-free pseudo-wild type variant (C38A C52V); and a core-repacked variant of the Cys-free variant (T19V L41V C38A C52V). These assignments enable functional and dynamic studies of wild-type and Cys-free variants of Rop. [ABSTRACT FROM AUTHOR]

TAR RNA binding protein (TRBP) is a double-stranded RNA binding protein involved in various biological processes like cell growth, development, death, etc. The protein exists as two isoforms TRBP2 and TRBP1. TRBP2 contains additional 21 amino acids at its N-terminus, which are proposed to be involved in its membrane localization, when compared to TRBP1. The resonance assignment (19-228) of the double-stranded RNA binding domains (dsRBD 1 and 2) of TRBP2 has been reported earlier. Here, we report 1H, 13C and 15N resonance assignment for dsRBD1 of TRBP2 (1-105) containing the additional N-terminal residues. This assignment will provide deeper insights to understand the effect of these residues on the structure and dynamics of TRBP2 and would therefore help in further elucidating the differences in the role of these isoforms. [ABSTRACT FROM AUTHOR]

The backbone assignment of medium-sized proteins is rarely as straightforward as that of small proteins, and thus often requires creative solutions. Here, we describe the application of a combination of standard 3D heteronuclear methods with CC(CO)NH and a variety of MUltiplicity Selective In-phase Coherence transfer (MUSIC) experiments. Both CC(CO)NH and MUSIC are, in theory, very powerful methods for the backbone assignment of proteins. Due to low sensitivity, their use has usually been linked to small proteins only. However, we found that combining CC(CO)NH and MUSIC experiments simplified the assignment of two challenging medium-sized proteins of 13 and 19.5 kDa, respectively. These methods are to some extent complementary to each other: CC(CO)NH acquired with a long isotropic mixing time can identify amino acids with large aliphatic side chains. Whereas the most sensitive MUSIC experiments identify amino acid types that cannot be detected by CC(CO)NH, comprising the residues with acid and amide groups, and aromatic rings in their side chains. Together these methods provide a means of identifying the majority of peaks in the 2D 15N HSQC spectrum which simplifies the backbone assignment work even for proteins, e.g., small kinases, whose standard spectra resulted in little spectral resolution and low signal intensities.

The C-terminal repeat domain of staphylocoagulase that is secreted by the S. aureus is believed to play an important role interacting with fibrinogen and promotes blood clotting. To study this interaction by NMR, full assignment of each amide residue in the HSQC spectrum was required. Despite of the short sequence of the repeat construct, the HSQC spectrum contained a substantial amount of overlapped and exchange broadened resonances, indicating little secondary or tertiary structure. This caused severe problems while using the conventional, amide based NMR method for the backbone assignment. With the growing interest in small apparently disordered proteins, these issues are being faced more frequently. An alternative strategy to improve the backbone assignment capability involved carbon direct detection methods. Circumventing the amide proton detection offers a larger signal dispersion and more uniform signal intensity. For peptides with higher concentrations and in combination with the cold carbon channels of new cryoprobes, higher fields, and sufficiently long relaxation times, the disadvantage of the lower sensitivity of the C nucleus can be overcome. Another advantage of this method is the assignment of the proline backbone residues. Complete assignment with the carbon-detected strategy was achieved with a set of only two 3D, one 2D, and a HNCO measurement, which was necessary to translate the information to the HSQC spectrum. [ABSTRACT FROM AUTHOR]

NSD3 is a histone H3 methyltransferase that plays an important role in chromatin biology. A construct containing the methyltransferase domain encompassing residues Q1049-K1299 of human NSD3 was obtained and biochemical activity was demonstrated using histone as a substrate. Here we report the backbone HN, N, Cα, C′, and side chain Cβ assignments of the construct in complex with S-adenosyl- l-methionine (SAM). Based on these assignments, secondary structures of NSD3/SAM complex in solution were determined. [ABSTRACT FROM AUTHOR]

TROSY-based triple resonance experiments are essential for protein backbone assignment of large biomolecular systems by solution NMR spectroscopy. In a survey of the current Bruker pulse sequence library for TROSY-based experiments we found that several sequences were plagued by artifacts that affect spectral quality and hamper data analysis. Specifically, these experiments produce sidebands in the C( t ) dimension with inverted phase corresponding to H resonance frequencies, with approximately 5% intensity of the parent C crosspeaks. These artifacts originate from the modulation of the H frequency onto the resonance frequency of Cα and/or Cβ and are due to 180° pulses imperfections used for H decoupling during the C( t ) evolution period. These sidebands can become severe for CA, CA and/or CB, CB correlation experiments such as TROSY-HNCACB. Here, we implement three alternative decoupling strategies that suppress these artifacts and, depending on the scheme employed, boost the sensitivity up to 14% on Bruker spectrometers. A class of comparable Agilent/Varian pulse sequences that use WALTZ16 H decoupling can also be improved by this method resulting in up to 60-80% increase in sensitivity. [ABSTRACT FROM AUTHOR]

Acinetobacter baumannii is a multidrug-resistant opportunistic pathogen which induces the cytotoxicity of host cells by nosocomial infections. Peptidoglycan-associated lipoprotein (Pal) is one component of Tol-Pal system, which is involved in maintaining the integrity and stability of the outer membrane (OM) as well as the virulence of bacterial pathogens. Pal is composed of N-terminal hydrophobic domain anchoring to the OM and C-terminal OmpA-like domain interacting with peptidoglycan. Herein, we report the preparation of protein sample and the backbone assignment of recombinant OmpA-like domain of Pal protein from Acinetobacter baumannii (AbPal-71). All the backbone chemical shifts of AbPal-71 (Cα, Cβ, CO, HN, and N) were completely assigned and the secondary structure was estimated from the assigned chemical shifts. This result shows that AbPal-71 is a typical OmpA-like fold, which consists of three α-helices and four β-strands. Based on this NMR spectroscopic results, the three dimensional structural study and the interaction study between AbPal-71 and peptidoglycan are in progress.

MJ0754 is an unknown hypothetical protein from hyperthermophilic archaeon Methanococcus jannaschii DSM 2661. Here we report the protein purification and NMR spectroscopic study of the N-terminal deleted truncated form of recombinant MJ0754 protein (Δ10-MJ0754). We aquired 3D NMR spectra and assigned all the backbone chemical shifts including Cα, Cβ, CO, HN, and N of Δ10-MJ0754. The secondary structure of Δ10-MJ0754 was estimated from the assigned backbone chemical shifts. This NMR result is very useful for further structural and functional study of MJ0754 protein.

Acinetobacter baumannii is a multiple drug resistant pathogen that causes pneumonia, bacteremia, wound infections and urinary tract infections in immunocompromised patients. Outer membrane protein A of Acinetobacter baumannii (AbOmpA) is a major surface protein and induces host cell death. AbOmpA is supposed to be composed of N-terminal β-barrel transmembrane domain and C-terminal periplasmic domain. The periplasmic domain of AbOmpA forms an OmpA-like fold, which is involved in the non-covalent interaction with peptidoglycan. However, its three dimensional structure is not determined yet. Here, we report the cloning, expression, purification and NMR spectroscopy study of recombinant AbOmpA periplasmic domain (AbOmpA-PD). The NMR spectrum of AbOmpA-PD is well dispered and almost signals exhibit homogeneous, which allow us to assign the backbone signals thoroughly. This study provides a clue for structural study of AbOmpA-PD.

Mst1 and Mst2 (Mammalian Sterile 20-like kinase 1 and 2) are pro-apoptotic protein kinases and involved in cell proliferation and survival. The C-termini of Mst1 and Mst contain a protein-protein interaction domain, named SARAH (Sav/Rassf/Hpo), which is found in three classes of eukaryotic tumour suppressors, Salvador, Rassf, and Hippo. The interaction of these SARAH domains controls apoptosis and cell cycle arrest. Moreover, Mst2 SARAH domain is known to interact with Raf-1, resulting in the suppression of apoptosis. In this study, we describe the sample preparation and NMR study of SARAH domain from Mst2 kinase. The gel-filtration chromatography shows that the SARAH domain of Mst2 forms a homodimer in solution. The NMR spectrum of Mst2 SARAH domain exhibit well-dispersed and homogeneous signals, which enable us to assign the backbone signals completely. These results provide a useful information for the structural and functional study of Mst2 SARAH domain.

Aberrant NSD2 methyltransferase activity is implicated as the oncogenic driver in multiple myeloma, suggesting opportunities for novel therapeutic intervention. The methyltransferase activity of NSD2 resides in its catalytic SET domain, which is conserved among most lysine methyltransferases. Here we report the backbone $$\hbox {H}^{\mathrm{N}}$$ , N, C $$^{\prime }$$ , $$\hbox {C}^\alpha$$ and side-chain $$\hbox {C}^\beta$$ assignments of a 25 kDa NSD2 SET domain construct, spanning residues 991-1203. A chemical shift analysis of C $$^{\prime }$$ , $$\hbox {C}^\alpha$$ and $$\hbox {C}^\beta$$ resonances predicts a secondary structural pattern that is in agreement with homology models. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) is a powerful tool to interrogate protein structure and dynamics residue by residue. However, the prerequisite chemical-shift assignment remains a bottleneck for large proteins due to the fast relaxation and the frequency degeneracy of the 13Cα nuclei. Herein, we present a covariance NMR strategy to assign the backbone chemical shifts by using only HN(CO)CA and HNCA spectra that has a high sensitivity even for large proteins. By using the peak linear correlation coefficient (LCC), which is a sensitive probe even for tiny chemical-shift displacements, we correctly identify the fidelity of approximately 92 % cross-peaks in the covariance spectrum, which is thus a significant improvement on the approach developed by Snyder and Brüschweiler (66 %) and the use of spectral derivatives (50 %). Thus, we calculate the 4D covariance spectrum from HN(CO)CA and HNCA experiments, in which cross-peaks with LCCs above a universal threshold are considered as true correlations. This 4D covariance spectrum enables the sequential assignment of a 42 kDa maltose binding protein (MBP), in which about 95 % residues are successfully assigned with a high accuracy of 98 %. Our LCC approach, therefore, paves the way for a residue-by-residue study of the backbone structure and dynamics of large proteins. [ABSTRACT FROM AUTHOR]

Traditional Nuclear Magnetic Resonance (NMR) assignment procedures for proteins rely on preliminary peak-picking to identify and label NMR signals. However, such an approach has severe limitations when signals are erroneously labeled or completely neglected. The consequences are especially grave for proteins with substantial peak overlap, and mistakes can often thwart entire projects. To overcome these limitations, we previously introduced an assignment technique that bypasses traditional pick peaking altogether. Covariance Sequential Correlation Maps (COSCOMs) transform the indirect connectivity information provided by multiple 3D backbone spectra into direct (H, N) to (H, N) correlations. Here, we present an updated method that utilizes a single four-dimensional spectrum rather than a suite of three-dimensional spectra. We demonstrate the advantages of 4D-COSCOMs relative to their 3D counterparts. We introduce improvements accelerating their calculation. We discuss practical considerations affecting their quality. And finally we showcase their utility in the context of a 52 kDa cyclization domain from a non-ribosomal peptide synthetase. [ABSTRACT FROM AUTHOR]

Analysis of protein NMR data involves the assignment of resonance peaks in a number of multidimensional data sets. To establish resonance assignment a three-dimensional search is used to match a pair of common variables, such as chemical shifts of the same spin system, in different NMR spectra. We show that by displaying the variables to be compared in two-dimensional plots the process can be simplified. Moreover, by utilizing a fast Fourier transform cross-correlation algorithm, more common to the field of image registration or pattern matching, we can automate this process. Here, we use sequential NMR backbone assignment as an example to show that the combination of correlation plots and segmented pattern matching establishes fast backbone assignment in fifteen proteins of varying sizes. For example, the 265-residue RalBP1 protein was 95.4 % correctly assigned in 10 s. The same concept can be applied to any multidimensional NMR data set where analysis comprises the comparison of two variables. This modular and robust approach offers high efficiency with excellent computational scalability and could be easily incorporated into existing assignment software. [ABSTRACT FROM AUTHOR]

Intrinsically disordered proteins (IDPs) are a class of highly flexible proteins whose characterization by NMR spectroscopy is complicated by severe spectral overlaps. The development of experiments designed to facilitate the sequence-specific assignment procedure is thus very important to improve the tools for the characterization of IDPs and thus to be able to focus on IDPs of increasing size and complexity. Here, we present and describe the implementation of a set of novel H-detected 5D experiments, (HACA)CON(CACO)NCO(CA)HA, BT-(H)NCO(CAN)CONNH and BT-HN(COCAN)CONNH, optimized for the study of highly flexible IDPs that exploit the best resolved correlations, those involving the carbonyl and nitrogen nuclei of neighboring amino acids, to achieve sequence-specific resonance assignment. Together with the analogous recently proposed pulse schemes based on C detection, they form a complete set of experiments for sequence-specific assignment of highly flexible IDPs. Depending on the particular sample conditions (concentration, lifetime, pH, temperature, etc.), these experiments present certain advantages and disadvantages that will be discussed. Needless to say, that the availability of a variety of complementary experiments will be important for accurate determination of resonance frequencies in complex IDPs. [ABSTRACT FROM AUTHOR]

The backbone assignment of medium-sized proteins is rarely as straightforward as that of small proteins, and thus often requires creative solutions. Here, we describe the application of a combination of standard 3D heteronuclear methods with CC(CO)NH and a variety of MUltiplicity Selective In-phase Coherence transfer (MUSIC) experiments. Both CC(CO)NH and MUSIC are, in theory, very powerful methods for the backbone assignment of proteins. Due to low sensitivity, their use has usually been linked to small proteins only. However, we found that combining CC(CO)NH and MUSIC experiments simplified the assignment of two challenging medium-sized proteins of 13 and 19.5 kDa, respectively. These methods are to some extent complementary to each other: CC(CO)NH acquired with a long isotropic mixing time can identify amino acids with large aliphatic side chains. Whereas the most sensitive MUSIC experiments identify amino acid types that cannot be detected by CC(CO)NH, comprising the residues with acid and amide groups, and aromatic rings in their side chains. Together these methods provide a means of identifying the majority of peaks in the 2D 15N HSQC spectrum which simplifies the backbone assignment work even for proteins, e.g., small kinases, whose standard spectra resulted in little spectral resolution and low signal intensities. [ABSTRACT FROM AUTHOR]

NMR assignment of intrinsically disordered proteins (IDPs) by conventional HN-detected methods is hampered by the small dispersion of the amide protons chemical shifts and exchange broadening of amide proton signals. Therefore several alternative assignment strategies have been proposed in the last years. Attempting to seize that dispersion of C′ and N chemical shifts holds even in IDPs, we recently proposed two C-detected experiments to directly correlate the chemical shifts of two consecutive C′-N groups in proteins, i.e. without mediation of other nuclei. Main drawback of these experiments is the interruption of the connection at prolines. Here we present new C-detected experiments to correlate consecutive C′-N groups in IDPs, hacacoNcaNCO and hacaCOncaNCO, that overcome this limitation. Moreover, the experiments provide recognition of glycine residues, thereby facilitating the assignment process. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two novel reduced dimensionality tailored HN(C)N experiments are presented. [•] Superior in terms of peak dispersion and helps to resolve the ambiguities arising because of 15N shift degeneracy. [•] Superior in terms of relative ease and speed of determining the sequential connectivities. [•] The ensuing assignment protocol has been presented. [•] The experiments are particularly useful when two sequential HSQC peaks have nearly identical 15N chemical shifts. [ABSTRACT FROM AUTHOR]

Sequence specific resonance assignment of proteins forms the basis for variety of structural and functional proteomics studies by NMR. In this context, an efficient standalone method for rapid assignment of backbone (H, N, C and C′) resonances of proteins has been presented here. Compared to currently available strategies used for the purpose, the method employs only a single reduced dimensionality experiment-(4,3)D-hn COCANH and exploits the linear combinations of backbone (C and C′) chemical shifts to achieve a dispersion relatively better compared to those of individual chemical shifts (see the text). The resulted increased dispersion of peaks-which is different in sum (CA + CO) and difference (CA − CO) frequency regions-greatly facilitates the analysis of the spectrum by resolving the problems (associated with routine assignment strategies) arising because of degenerate amide N and backbone C chemical shifts. Further, the spectrum provides direct distinction between intra- and inter-residue correlations because of their opposite peak signs. The other beneficial feature of the spectrum is that it provides: (a) multiple unidirectional sequential ( i→ i + 1) N and C correlations and (b) facile identification of certain specific triplet sequences which serve as check points for mapping the stretches of sequentially connected HSQC cross peaks on to the primary sequence for assigning the resonances sequence specifically. On top of all this, the F- F planes of the spectrum corresponding to sum (CA + CO) and difference (CA − CO) chemical shifts enable rapid and unambiguous identification of sequential HSQC peaks through matching their coordinates in these two planes (see the text). Overall, the experiment presented here will serve as an important backbone assignment tool for variety of structural and functional proteomics and drug discovery research programs by NMR involving well behaved small folded proteins (MW < 15 kDa) or a range of intrinsically disordered proteins.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Two novel 3D C-detected experiments, hNcocaNCO and hnCOcaNCO, are proposed to facilitate the resonance assignment of intrinsically disordered proteins. The experiments correlate the N and C′ chemical shifts of two consecutive amide moieties without involving other nuclei, thus taking advantage of the good dispersion shown by the N-C′ correlations, even for proteins that lack a well defined tertiary structure. The new pulse sequences were successfully tested using Nupr1, an intrinsically disordered protein of 93 residues. [ABSTRACT FROM AUTHOR]

Highlights: [•] The loop between S0 and S1 of BK channel was overexpressed and purified in DPC. [•] NMR studies indicated BK-IS1 contained two helices connected by a flexible loop. [•] Mg2+ titration of BK-IS1 indicated two possible binding sites of divalent ions. [ABSTRACT FROM AUTHOR]

Backbone dynamics and conformational properties of drug peptide salmon calcitonin have been studied in aqueous solution using nuclear magnetic resonance (NMR). Although salmon calcitonin (sCT) is largely unfolded in solution (as has been reported in several circular dichroism studies), the secondary Hα chemical shifts and three bond HN-Hα coupling constants indicated that most of the residues of the peptide are populating the α-helical region of the Ramachandran ( ϕ, ψ) map. Further, the peptide in solution has been found to exhibit multiple conformational states exchanging slowly on the NMR timescale (102-103 s−1), inferred by the multiple chemical shift assignments in the region Leu4-Leu12 and around Pro23 (for residues Gln20-Tyr22 and Arg24). Possibly, these slowly exchanging multiple conformational states might inhibit symmetric self-association of the peptide and, in part, may account for its reduced aggregation propensity compared with human calcitonin (which lacks this property). The 15N NMR-relaxation data revealed (i) the presence of slow (microsecond-to-millisecond) timescale dynamics in the N-terminal region (Cys1-Ser5) and core residues His17 and Asn26 and (ii) the presence of high frequency (nanosecond-to-picosecond) motions in the C-terminal arm. Put together, the various results suggested that (i) the flexible C-terminal of sCT (from Thr25-Thr31) is involved in identification of specific target receptors, (ii) whereas the N-terminal of sCT (from Cys1-Gln20) in solution - exhibiting significant amount of conformational plasticity and strong bias towards biologically active α-helical structure - facilitates favorable conformational adaptations while interacting with the intermembrane domains of these target receptors. Thus, we believe that the structural and dynamics features of sCT presented here will be useful guiding attributes for the rational design of biologically active sCT analogs. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The characterization of intrinsically disordered proteins (IDPs) by NMR spectroscopy is made difficult by the extensive spectral overlaps. To overcome the intrinsic low-resolution of the spectra the introduction of high-dimensionality experiments is essential. We present here a set of high-resolution experiments based on direct C-detection which proved useful in the assignment of α-synuclein, a paradigmatic IDP. In particular, we describe the implementation of 4D HCBCACON, HCCCON, HCBCANCO, 4/5D HNCACON and HNCANCO and 3/4D HCANCACO experiments, specifically tailored for spin system identification and backbone resonances sequential assignment. The use of non-uniform-sampling in the indirect dimension and of the H-flip approach to achieve longitudinal relaxation enhancement rendered the experiments very practical. [ABSTRACT FROM AUTHOR]

Four novel 5D (HACA(N)CONH, HNCOCACB, (HACA)CON(CA)CONH, (H)NCO(NCA)CONH), and one 6D ((H)NCO(N)CACONH) NMR pulse sequences are proposed. The new experiments employ non-uniform sampling that enables achieving high resolution in indirectly detected dimensions. The experiments facilitate resonance assignment of intrinsically disordered proteins. The novel pulse sequences were successfully tested using δ subunit (20 kDa) of Bacillus subtilis RNA polymerase that has an 81-amino acid disordered part containing various repetitive sequences. [ABSTRACT FROM AUTHOR]

Abstract: We present here an improvisation of HNN (Panchal, Bhavesh et al., 2001) called RD 3D HNCAN for backbone (HN, CA and 15N) assignment in both folded and unfolded proteins. This is a reduced dimensionality experiment which employs CA chemical shifts to improve dispersion. Distinct positive and negative peak patterns of various triplet segments along the polypeptide chain observed in HNN are retained and these provide start and check points for the sequential walk. Because of co-incrementing of CA and 15N, peaks along one of the dimensions appear at sums and differences of the CA and 15N chemical shifts. This changes the backbone assignment protocol slightly and we present this in explicit detail. The performance of the experiment has been demonstrated using Ubiquitin and Plasmodium falciparum P2 proteins. The experiment is particularly valuable when two neighboring amino acid residues have nearly identical backbone 15N chemical shifts. [Copyright &y& Elsevier]

For micro-crystalline proteins, solid-state nuclear magnetic resonance spectroscopy of perdeuterated samples can provide spectra of unprecedented quality. Apart from allowing to detect sparsely introduced protons and thereby increasing the effective resolution for a series of sophisticated techniques, deuteration can provide extraordinary coherence lifetimes-obtainable for all involved nuclei virtually without decoupling and enabling the use of scalar magnetization transfers. Unfortunately, for fibrillar or membrane-embedded proteins, significantly shorter transverse relaxation times have been encountered as compared to micro-crystalline proteins despite an identical sample preparation, calling for alternative strategies for resonance assignment. In this work we propose an approach towards sequential assignment of perdeuterated proteins based on long-range H/C Cross Polarization transfers. This strategy gives rise to H/N-separated correlations involving C, C, and CO chemical shifts of both, intra- and interresidual contacts, and thus connecting adjacent residues independent of transverse relaxation times. [ABSTRACT FROM AUTHOR]

Development of efficient strategies and automation represent important milestones of progress in rapid structure determination efforts in proteomics research. In this context, we present here an efficient algorithm named as AUTOBA (Automatic Backbone Assignment) designed to automate the assignment protocol based on HN(C)N suite of experiments. Depending upon the spectral dispersion, the user can record 2D or 3D versions of the experiments for assignment. The algorithm uses as inputs: (i) protein primary sequence and (ii) peak-lists from user defined HN(C)N suite of experiments. In the end, one gets H, N, C and C′ assignments (in common BMRB format) for the individual residues along the polypeptide chain. The success of the algorithm has been demonstrated, not only with experimental spectra recorded on two small globular proteins: ubiquitin (76 aa) and M-crystallin (85 aa), but also with simulated spectra of 27 other proteins using assignment data from the BMRB. [ABSTRACT FROM AUTHOR]

Abstract: MiRP1 (MinK related protein 1) is a membrane protein in the KCNE family. It can associate with and modulate various voltage gated potassium channels. Mutations in human MiRP1 have been found to cause many congenital and acquired long QT syndromes, which are potentially life-threatening cardiac arrhythmias. Here, human MiRP1 was over-expressed in Escherichia coli, purified and eluted into different detergents. Two dimensional 1H–15N correlated solution nuclear magnetic resonance (NMR) spectra of the human MiRP1 in four different detergent micelles indicated that high resolution solution NMR spectrum can be obtained for human MiRP1 in detergent lyso-myristoylphosphatidylglycerol (LMPG). Circular dichroism (CD) spectroscopy of human MiRP1 indicated a high content of alpha-helical secondary structure in LMPG. Backbone assignments of most MiRP1 residues were achieved through a series of triple resonance NMR experiments. Secondary structure analysis based on backbone chemical shifts showed several stretches of alpha-helices along the primary sequence of MiRP1 in LMPG. [ABSTRACT FROM AUTHOR]

An efficient high-throughput method for sequential assignment of backbone ¹HN and 15N, atoms in less than a day (using 2-4 2D spectra; total data collection in 4-8 h) has been proposed here. This is based on sequential correlations and specific patterns of peaks around the glycines, alanines, serines/threonines (internal check points) observable in the F1-F3 projection planes of the 3D-HN(C)N spectral variants. The F2-F3 projection planes of the spectra provide unique identification of the check points. The protocol has been demonstrated on two 13C/15N-labelled proteins: ubiquitin and calbindin-D9k. In either case complete HN and 15N backbone assignments were obtained in less than a day each. The method would be valuable for NMR structural studies of small, well-folded proteins. [ABSTRACT FROM AUTHOR]

Abstract: Time-saving in data acquisition is a major thrust of NMR pulse sequence development in the context of structural proteomics research. The conventional HNCA and HN(CA)CO pulse sequences, routinely used for sequential backbone assignment, have the limitation that they cannot distinguish inter- and intra-residue correlations. In order to remove this ambiguity, one has to record HNCO and HN(CO)CA or sequential HNCA experiments which provide unambiguous information of sequential correlations. However, this almost doubles the experimental time. Besides, they require repeated scanning through the 15N planes to search for the matching peaks along the carbon dimension. In this background, we present here two pulse sequences, termed as hncoCANH and hnCOcaNH that lead to spectra equivalent to HNCA and HN(CA)CO spectra, respectively, but with direct distinction of inter- and intra-residue peaks; these occur with opposite signs in the new experiments. The two pulse sequences have been derived by simple modification of the previously described HN(C)N pulse sequence [Panchal et al., J. Biomol. NMR 20 (2001) 135–147] to frequency-label 13Cα or 13C′ instead of 15N during the t 1 period. Like HN(C)N, these spectra also exhibit special patterns of self and sequential peaks around glycines and prolines, which enable direct identification of certain triplets of residues and thus provide internal checks during the sequential assignment walk. The spectra enable rapid and unambiguous assignment of HN, 15N and 13Cα (or 13C′) in a single experiment, and thus would be of great value in high-throughput structural proteomics. [ABSTRACT FROM AUTHOR]