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Elaiophylin (Ela), a unique 16‐membered symmetric macrodiolide antibiotic, displays broad biological activity. Two rare 2‐deoxy‐l‐fucose moieties at the ends of Ela are critical for its activity. Previously, elaiophylin glycosyltransferase (ElaGT) was identified as the enzyme that is responsible for the symmetric glycosylation of Ela, acting as a potential enzymatic tool for enhancing the diversity and activity of Ela. However, a symmetric catalytic mechanism has never been reported for a glycosyltransferase (GT). To explore the catalytic mechanism, the structure of ElaGT was determined in four forms: the apo form and Ela‐bound, thymidine diphosphate‐bound and uridine diphosphate‐bound forms. In the Ela‐bound structure, two ElaGTs form a 'face‐to‐face' C2‐symmetric homodimer with a continuous acceptor‐binding pocket, allowing a molecule of Ela to shuffle through. Interestingly, this dimer interface resembles that of the activator‐dependent GT EryCIII with its activator EryCII. Sequence analysis also indicates that ElaGT belongs to the activator‐dependent GT family, but no putative activator has been identified in the Ela gene cluster. It was then found that the ElaGT homodimer may utilize this 'face‐to‐face' arrangement to stabilize the Ela‐binding loops on the interface and to simultaneously allosterically regulate the catalytic center. Therefore, these structures present a novel self‐activating model for symmetric sugar transfer in the GT family and a new potential regulation site for substrate specificity. [ABSTRACT FROM AUTHOR]

MAS1 from marine Streptomyces sp. strain W007 belongs to the bacterial lipase I.7 subfamily and is characterized as a thermostable and nonregiospecific lipase. To shed light on the catalytic mechanism of MAS1, we determined its crystal structure with closed conformation in two crystal forms at 2.3 Å resolution. MAS1 adopts the canonical α/β hydrolase core fold with its catalytic triad being formed by S109, D200 and H232. Structural analysis and biochemical assays revealed that disulfide bonds and salt bridges play a vital role in the thermostability of MAS1. In addition, we discovered that the replacement of H108 with a tryptophan converts MAS1 from a nonregiospecific to an sn-1,3-specific lipase, suggesting the functional importance of the second position from the conserved pentapeptide motif in defining the regiospecificity of MAS1. Our present study provides insights into the molecular basis for the thermostability and regiospecificity of MAS1, and it may aid in the rational design of thermostable or regiospecific lipases for potential industrial applications. Database Structural data are available in the Protein Data Bank database under the accession numbers and . [ABSTRACT FROM AUTHOR]

SNX25, a regulator of GPCR signaling-phox-homology ( PX) domain containing sorting nexin ( SNX) member, has been proposed to be involved in the lysosomal degradation of the transforming growth factor β receptor and the development of temporal lobe epilepsy. Targeting to the endosomal membranes by the specific binding of phosphorylated phosphatidylinositols (PIPs) through the PX domain is critical for the function of SNXs. However, the mechanism for SNX25- PX targeting to the endosomes remains unclear. Here, we demonstrate that the PX domain of zebrafish SNX25 ( zSNX25- PX) is capable of binding to PI3P only in its dimeric form. We also present the crystal structure of zSNX25- PX. Combined with biochemical experiments, we further identify a potential PI3P-binding region and propose a novel PI-binding model based on dimerization in the PX domain of SNXs. [ABSTRACT FROM AUTHOR]

Monoacylglycerol and diacylglycerol lipases are industrially interesting enzymes, due to the health benefits that arise from the consumption of diglycerides compared to the traditional triglyceride oils. Most lipases possess an α-helix (lid) directly over the catalytic pocket which regulates the activity of the enzyme. Generally, lipases exist in active and inactive conformations, depending on the positioning of this lid subdomain. However, lipase SMG1, a monoacylglycerol and diacylglycerol specific lipase, has an atypical activation mechanism. In the present study we were able to prove by crystallography, in silico analysis and activity tests that only two positions, residues 102 and 278, are responsible for a gating mechanism that regulates the active and inactive states of the lipase, and that no significant structural changes take place during activation except for oxyanion hole formation. The elucidation of the gating effect provided data enabling the rational design of improved lipases with 6-fold increase in the hydrolytic activity toward diacylglycerols, just by providing additional substrate stabilization with a single mutation (F278N or F278T). Due to the conservation of F278 among the monoacylglycerol and diacylglycerol lipases in the Rhizomucor miehei lipase-like family, the gating mechanism described herein might represent a general mechanism applicable to other monoacylglycerol and diacylglycerol lipases as well. [ABSTRACT FROM AUTHOR]

Flower-like MoS 2 spheres were successfully prepared via a facile hydrothermal method. The effects of excess sulfur on the formation of MoS 2 were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD pattern showed that the preferential orientation of the flower-like hexagonal 2H–MoS 2 spheres was the (002) plane, and I 002 / I 100 ratio values indicated that the (002) plane grew more completely than the (100) plane with increasing S/Mo ratio. The FESEM images revealed that the sheet thickness of the MoS 2 spheres increased to ~30 nm with increasing S/Mo ratio, exposing more edges on the nanosheets of the MoS 2 spheres. Photocatalytic properties of the products were studied, and the results showed that the MoS 2 sample with a S/Mo ratio of 2.75 exhibited the highest degradation rate constant and methylene blue degradation rate under 90 min visible light irradiation. The results showed that the enhancement of photocatalytic activity originated from increasing exposed area of the {100} facets with increasing S/Mo ratio under the hydrothermal environment. [ABSTRACT FROM AUTHOR]

Immunosuppression associated with infections of nematode parasites has been documented. Cysteine protease inhibitor (CPI) released by the nematode parasites is identified as one of the major modulators of host immune response. In this report, we demonstrated that the recombinant CPI protein of Ascaris lumbricoides (Al-CPI) strongly inhibited the activities of cathepsin L, C, S, and showed weaker effect to cathepsin B. Crystal structure of Al-CPI was determined to 2.1 Å resolution. Two segments of Al-CPI, loop 1 and loop 2, were proposed as the key structure motifs responsible for Al-CPI binding with proteases and its inhibitory activity. Mutations at loop 1 and loop 2 abrogated the protease inhibition activity to various extents. These results provide the molecular insight into the interaction between the nematode parasite and its host and will facilitate the development of anthelmintic agents or design of anti-autoimmune disease drugs. [ABSTRACT FROM AUTHOR]

Abstract: Human glucokinase (GK) plays an important role in glucose homeostasis. An E339K mutation in GK was recently found to be associated with hyperglycemia. It showed lower enzyme activity and impaired protein stability compared to the wild-type enzyme. Here, we present the crystal structure of E339K GK in complex with glucose. This mutation results in a conformational change of His416, spatially interfering with adenosine-triphosphate (ATP) binding. Furthermore, Ser411 at the ATP binding site is phosphorylated and then hydrogen bonded with Thr82, physically blocking the ATP binding. These findings provide structural basis for the reduced activity of this mutant. [Copyright &y& Elsevier]

AgI nanoparticles decorated with ZnO flower-like composites were successfully synthesized via citric acid-induced hydrothermal reaction and subsequent chemical deposition in the presence of ammonium hydroxide. The effects of AgI-loading content and the piezoelectric effect of ZnO were investigated using different technologies. The crystal structures and optical and photocatalytic properties revealed that the AgI particles were successfully loaded on the flower-like ZnO through the directed diffusion process of charge-induced deposition. Results also showed that the band gap of the AgI/ZnO composite located between those of the ZnO and the AgI, which was consistent with the theoretic simulation. The degradation rate of RhB induced by the AgI/ZnO composites was three times larger than that of AgI, and the heterojunction exhibited high photocatalytic degradation efficiency for MO and TC. Besides, the photodegradation efficiency remained high after six times. Radical scavenger experiments implied that e− and h+ played important roles in the photocatalytic process. The photodegradation time was considerably shortened while maintaining increased degradation efficiency after adding ultrasonic vibration due to the rapid separation of carriers caused by the piezo-photocatalysis coupling effect. • AgI/ZnO heterostructures were synthesized by a simple chemical deposition. • High degradation efficiency and excellent reusing activity was obtained. • It is due to rapid separation of dominant e− and h+ from AgI/ZnO heterostructure. • Degradation time was greatly shortened under ultrasonic vibration. [ABSTRACT FROM AUTHOR]

ω-transaminase has attracted growing attention for chiral amine synthesis, although it commonly suffers from severe by-product inhibition. ω-transaminase CrmG is critical for the biosynthesis of Caerulomycin A, a natural product that possesses broad bioactivity, including immunosuppressive and anti-cancer. Compared to L-Arg, amino donor L-Glu, L-Gln or L-Ala is more preferred by CrmG. In this study, we determined the crystal structure of CrmG in complex with amino donor L-Arg, unveiling the detailed binding mode. Specifically, L-Arg exhibits an extensive contact with aromatic residues F207 and W223 on the roof of CrmG active site via cation-π network. This interaction may render the deamination by-product of L-Arg to be an inhibitor against PMP-bound CrmG by stabilizing its flexible roof, thus reducing the reactivity of L-Arg as an amino donor for CrmG. These data provide further evidence to support our previous proposal that CrmG can overcome inhibition from those by-products that are not able to stabilize the flexible roof of active site in PMP-bound CrmG. Thus, our result can not only facilitate the biosynthesis of CRM A but also be beneficial for the rational design of ω-transaminase to bypass by-product inhibition. • Crystal structure of CrmG in complex with amino donor L-Arg is reported. • L-Arg interacts with the roof of CrmG active site via unique cation-π network. • The interaction with the roof impairs reactive efficiency of L-Arg as CrmG amino donor. [ABSTRACT FROM AUTHOR]

Sodium cobalt oxides (Na x CoO 2 , denoted as NCO) have attracted considerable attentions as the promising candidate of high-temperature thermoelectric materials because of their high thermoelectric power, high thermal stability and non-toxicity. The performances of NCO materials are dependent on their crystal structure. In this paper, the crystal structure and thermoelectric properties for NCO samples prepared by the solid state method under different sintering temperatures are discussed. Importantly, a phase transformation is discovered in NCO ceramics by TG-DTA analysis. The structural transformation is probably caused by Na volatilization at high temperature. With increasing sintering temperature, the Na ion concentration decreases, and the valence state of the Co ions increases, which can influence the carriers transport properties. In addition, a large number of grain boundaries generated by the fine grain prepared under low sintering temperature can effectively decrease the thermal conductivity. Thus, the figure-of-merit ZT value can be enhanced by the large Seebeck coefficient and low thermal conductivity in the low-temperature phase. [ABSTRACT FROM AUTHOR]

The estrogen-related receptor (ERR) family members are reported to bind DNA elements as either monomer or dimer. However, to date, only one solution NMR structure of ERRβ in complex with a half-site DNA element has been reported. To better understand the DNA regulation mechanism, we determined the crystal structure of ERRγ-DBD bound to a natural DR1 element in Pla2g12b promoter to 2.2 Å resolution. Combined with biochemical assays, we show that ERRγ acts as a dimer and the C-terminal extension region undergoes conformational rearrangement when binding to the downstream DR1 element. In addition, the T-box region on the dimerization interface exhibits unique main-chain conformation. Thus, our structure presents a novel dimer interface for NR binding on DR1 DNA and provides a molecular basis for understanding the homodimer organization of ERR on DR1 elements. • We determined the first dimeric structure of ERRγ-DBD in complex with a DR1 element. • The CTE tail of ERRγ-DBD undergoes conformational rearrangement when binding to the downstream DR1 element. • The T-box conformation of ERRγ-DBD is unique on the dimer interface when binding to DR1. [ABSTRACT FROM AUTHOR]

Abstract: 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the NADPH dependent interconversion of inactive cortisone to active cortisol. Excess 11β-HSD1 or cortisol leads to insulin resistance and metabolic syndrome in animal models and in humans. Inhibiting 11β-HSD1 activity signifies a promising therapeutic strategy in the treatment of Type 2 diabetes and related diseases. Herein, we report two highly potent and selective small molecule inhibitors of human 11β-HSD1. While compound 1, a sulfonamide, functions as a simple substrate competitive inhibitor, compound 2, a triazole, shows the kinetic profile of a mixed inhibitor. Co-crystal structures reveal that both compounds occupy the 11β-HSD1 catalytic site, but present distinct molecular interactions with the protein. Strikingly, compound 2 interacts much closer to the cofactor NADP+ and likely modifies its binding. Together, the structural and kinetic analyses demonstrate two distinctive molecular inhibition mechanisms, providing valuable information for future inhibitor design. [Copyright &y& Elsevier]

Secreted phospholipases A2 (sPLA2) group IIE (GIIE) is involved in several biological events, such as lipid metabolism and possibly inflammation that may mainly depend on its catalytic reaction. We previously showed that Asn21 is a critical residue that contributes to the enzymatic activity of hGIIE, but the underlying mechanism is still not clear. Here, combined with crystal structures and mutagenesis studies of the Asn21Gly mutant, we demonstrate that Asn21 acts as a switch responsible for the calcium binding and the catalytic efficiency. Our results of the atypical feature of calcium binding in hGIIE not only provide clues to understand the molecular basis of its enzymatic activity and physiological function, but also confer improved specificity for potential inhibitor design of sPLA2. • sPLA2 GIIE is a Ca2+-dependent hydrolytic enzyme and contains two Ca binding sites. • N21 contributes to the catalytic efficiency of hGIIE. • N21G mutation can affect the second Ca (Ca2) binding. • N21 acts as a switch to regulate the Ca2 binding involved in the catalytic action. [ABSTRACT FROM AUTHOR]

Aflatoxin-oxidase (AFO), a newly discovered oxidase isolated from Armillariella tabescens , was reported to perform aflatoxin B1 (AFB1) detoxification through breaking the bisfuran ring of AFB1. However, based on sequence alignment, we found that AFO shares high sequence identities with dipeptidyl peptidase III (DPP III) family members. To understand the functions of AFO, we determined its crystal structures in the absence and presence of zinc, copper ion, and employed HPLC to test if AFO could cleave the substrates of DPP III. Our structures reveal that AFO contains the classic DPP III activity center and the HPLC results further confirm that AFO possesses the dipeptidyl peptidase activity. Therefore, AFO should belong to DPP III family. Interestingly, unlike reported classic DPP III structure that has a large domain movement upon substrate binding, the AFO structures all adopt the closed conformation, independent of substrate binding. This conformation characteristic of AFO may be related to its enzyme activities. Taken together, our results demonstrate that AFO is a dual activity enzyme with both aflatoxin-oxidase and dipeptidyl peptidase activities and its unique conformation feature expands our understanding on the mode of reaction for this enzyme family. [ABSTRACT FROM AUTHOR]

Lipases play an important role in physiological metabolism and diseases, and also have multiple industrial applications. Rational modification of lipase specificity may increase the commercial utility of this group of enzymes, but is hindered by insufficient mechanistic understanding. Here, we report the 2.0 Å resolution crystal structure of a mono- and di-acylglycerols lipase from Malassezia globosa ( Mg MDL2). Interestingly, residues Phe278 and Glu282 were found to involve in substrate recognition because mutation on each residue led to convert Mg MDL2 to a triacylglycerol (TAG) lipase. The Phe278Ala and Glu282Ala mutants also acquired ability to synthesize TAGs by esterification of glycerol and fatty acids. By in silicon analysis, steric hindrance of these residues seemed to be key factors for the altered substrate specificity. Our work may shed light on understanding the unique substrate selectivity mechanism of mono- and di-acylglycerols lipases, and provide a new insight for engineering biocatalysts with desired catalytic behaviors for biotechnological application. [ABSTRACT FROM AUTHOR]

Crystal size and microstructure are of great importance in determining the physical and chemical properties of functional materials, and refine powders, especially their assembled porous structures have potential application in ceramic fabrication, absorption, catalysts and drug delivery, due to their characters of high activity and large specific surface area. Herein, high temperature mixing method under hydrothermal condition (HTMM) was adapted to synthesize barium strontium titanate [(Ba, Sr)TiO 3 , BST] powders with various Ba/Sr ratios ( x = 0.5, 1.0, 3.0 and 4.0). In comparison with conventional hydrothermal synthesis (CHS), the effects of HTMM on grain refinement and porous structure formation were exclusively investigated. XRD and SEM results indicated that, in the given condition, BST powders prepared by HTMM were much smaller than that by CHS, especially at a lower Ba/Sr ratio. Additionally, assembled porous architectures were constructed by HTMM. It's believed that the high temperature mixing process and continuous rotation contributed to the grain refinement and assembled porous structure, respectively. The assumption was further confirmed through the synthesis of sodium niobate (NaNbO 3 ) powders by HTMM. It's demonstrated that HTMM is advantageous in preparation of refine powders and porous assembled architectures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crystal structures of RGS homology (RH) domains of SNX13 and SNX25 were reported. • Extended α4 and α5 helices mediate homodimerization of SNX13 RH domain. • Unique residue C362 on α6 helix triggers homodimerization of SNX25 RH domain. • RH domains of SNX-RH represent a novel non-canonical RH domain. As a subgroup of sorting nexins (SNXs) that contain regulator of G protein signaling homology (RH) domain, SNX-RH proteins, including SNX13, SNX14 and SNX25, were proposed to play bifunctional roles in protein sorting and GPCR signaling regulation. However, mechanistic details of SNX-RH proteins functioning via RH domain remain to be illustrated. Here, we delineate crystal structures of the RH domains of SNX13 and SNX25, revealing a homodimer of SNX13 RH domain mediated by unique extended α4 and α5 helices, and a thiol modulated homodimer of SNX25-RH triggered by a unique cysteine on α6 helix. Further studies showed that RH domains of SNX-RH do not possess binding capacity toward Gα subunits, owing to the lack of critical residues for interaction. Thus, this study identifies a group of novel non-canonical RH domains that can act as a dimerization module in sorting nexins, which provides structural basis for mechanism studies on SNX-RH protein functions. [ABSTRACT FROM AUTHOR]

The dengue virus NS2B-NS3 protease (NS2B-NS3p), an important antiviral target for drug development, has been reported to adopt an open or closed conformation in crystal structures with different NS2B C-terminus (NS2Bc) positioning. In solution, nevertheless, NS2B-NS3p forms a mixture of open, closed and maybe other intermediate conformations, which is difficult to characterize using conventional biophysical and biochemical techniques. In this study, we developed a new strategy to analyze these conformational changes using 19 F NMR spectroscopy. Low pH or bovine pancreatic trypsin inhibitor (BPTI) binding promote the conformation change from open to closed, showing the importance of charge forces in the interaction between NS2Bc and NS3p. The mutation H51A impairs the charge interaction and the pH dependence of the conformational changes. It stabilizes the open conformation, while the addition of BPTI still converts NS2B-NS3p from open to closed conformation. [ABSTRACT FROM AUTHOR]

Immunosuppression associated with infections of nematode parasites has been documented. Cysteine protease inhibitor (CPI) released by the nematode parasites is identified as one of the major modulators of host immune response. In this report, we demonstrated that the recombinant CPI protein of Ascaris lumbricoides (Al-CPI) strongly inhibited the activities of cathepsin L, C, S, and showed weaker effect to cathepsin B. Crystal structure of Al-CPI was determined to 2.1 Å resolution. Two segments of Al-CPI, loop 1 and loop 2, were proposed as the key structure motifs responsible for Al-CPI binding with proteases and its inhibitory activity. Mutations at loop 1 and loop 2 abrogated the protease inhibition activity to various extents. These results provide the molecular insight into the interaction between the nematode parasite and its host and will facilitate the development of anthelmintic agents or design of anti-autoimmune disease drugs. [ABSTRACT FROM AUTHOR]

Summary: Sphingosine kinase 1 (SphK1) is a lipid kinase that catalyzes the conversion of sphingosine to sphingosine-1-phosphate (S1P), which has been shown to play a role in lymphocyte trafficking, angiogenesis, and response to apoptotic stimuli. As a central enzyme in modulating the S1P levels in cells, SphK1 emerges as an important regulator for diverse cellular functions and a potential target for drug discovery. Here, we present the crystal structures of human SphK1 in the apo form and in complexes with a substrate sphingosine-like lipid, ADP, and an inhibitor at 2.0–2.3 Å resolution. The SphK1 structures reveal a two-domain architecture in which its catalytic site is located in the cleft between the two domains and a hydrophobic lipid-binding pocket is buried in the C-terminal domain. Comparative analysis of these structures with mutagenesis and kinetic studies provides insight into how SphK1 recognizes the lipid substrate and catalyzes ATP-dependent phosphorylation. [ABSTRACT FROM AUTHOR]

Abstract: The discovery, structure-based design, synthesis, and optimization of NIK inhibitors are described. Our work began with an HTS hit, imidazopyridinyl pyrimidinamine 1. We utilized homology modeling and conformational analysis to optimize the indole scaffold leading to the discovery of novel and potent conformationally constrained inhibitors such as compounds 25 and 28. Compounds 25 and 31 were co-crystallized with NIK kinase domain to provide structural insights. [Copyright &y& Elsevier]

Abstract: Monodispersed barium titanate (BT) nanopowders with perovskite structure were successfully prepared by a sol–hydrothermal method. The results obtained from X-ray diffraction (XRD) revealed that BT particles with single cubic phase were favorably formed with low alkalinity, whereas tetragonal phase was observed with the enhancement of the alkalinity. Furthermore, electronic microcopy observations demonstrated that spherical aggregates of nanocrystals in final BT products transformed into mesocrystals with circular shape, and then into single crystals with rectangular shape as the alkalinity was elevated from 0.2M to 1M, concurrent with the decrease in average particle size. A mechanism involving the Ba/Ti ratio in the initial solution was proposed to illustrate the transformation of morphology and formation of crystals. [Copyright &y& Elsevier]

Abstract: Most lipases contain a lid domain to shield the hydrophobic binding site from the water environment. The lid, mostly in helical form, can undergo a conformational change to expose the active cleft during the interfacial activation. Here we report the crystal structures of Malassezia globosa LIP1 (SMG1) at 1.45 and 2.60Å resolution in two crystal forms. The structures present SMG1 in its closed form, with a novel lid in loop conformation. SMG1 is one of the few members in the fungal lipase family that has been found to be strictly specific for mono- and diacylglycerol. To date, the mechanism for this substrate specificity remains largely unknown. To investigate the substrate binding properties, we built a model of SMG1 in open conformation. Based on this model, we found that the two bulky hydrophobic residues adjacent to the catalytic site and the N-terminal hinge region of the lid both may act as steric hindrances for triacylglycerols binding. These unique structural features of SMG1 will provide a better understanding on the substrate specificity of mono- and diacylglycerol lipases and a platform for further functional study of this enzyme. [Copyright &y& Elsevier]

Summary E-Cadherin is a major component of adherens junctions on cell surfaces. SNX16 is a unique member of sorting nexins that contains a coiled-coil (CC) domain downstream of the PX domain. We report here that SNX16 regulates the recycling trafficking of E-cadherin. We solved the crystal structure of PX-CC unit of SNX16 and revealed a unique shear shaped homodimer. We identified a novel PI3P binding pocket in SNX16 that consists of both the PX and the CC domains. Surprisingly, we showed that the PPII/α2 loop, which is generally regarded as a membrane insertion loop in PX family proteins, is involved in the E-cadherin binding with SNX16. We then proposed a multivalent membrane binding model for SNX16. Our study postulates a new mechanism for coordinated membrane binding and cargo binding for SNX family proteins in general, and provide novel insights into recycling trafficking of E-cadherin. [ABSTRACT FROM AUTHOR]