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A novel contoxin inhibitor of Kv 1.6 channel and nicotinic acetylcholine receptor (nACHR) subtypes are used to define a new family of conotoxins, named p114a that has a potent activity at the nACHR subtypes, as well as the voltage-gated potassium channel subtype. The results show that there exist many similarities between the middle loop of p114a and the second loop of many other conotoxins though it is the first conotoxin to affect both the activities simultaneously.

Conotoxins (CTXs), with their exquisite specificity and potency, have recently created much excitement as drug leads. However, like most peptides, their beneficial activities may potentially be undermined by susceptibility to proteolysis in vivo. By cyclizing the [alpha]-CTX MII by using a range of linkers, we have engineered peptides that preserve their full activity but have greatly improved resistance to proteolytic degradation. The cyclic MII analogue containing a seven-residue linker joining the N and C termini was as active and selective as the native peptide for native and recombinant neuronal nicotinic acetylcholine receptor subtypes present in bovine chromaffin cells and expressed in Xenopus oocytes, respectively. Furthermore, its resistance to proteolysis against a specific protease and in human plasma was significantly improved. More generally, to our knowledge, this report is the first on the cyclization of disulfide-rich toxins. Cyclization strategies represent an approach for stabilizing bioactive peptides while keeping their full potencies and should boost applications of peptide-based drugs in human medicine. conotoxins | drug delivery | molecular engineering

Research has been conducted on the peptide toxin isolated from a spider venom. The primary sequence and three-dimensional structure of this toxin have been investigated via the use of the NMR spectroscopy and the results indicate that in solution the molecule contains conformations produced by the cis/trans isomerization of its proline residue.

The trypsin inhibitor BSTI from Bombina bombina frog consists of 60 residues with five disulfide bonds and a secondary structure of four beta-strands arranged in two antiparallel beta-sheets. BSTI is folded into a disc shape with no hydrophobic core and the active site located in a loop made of 21-34 residues.

A study of immunodominant peptides corresponding to Tau(224-240) and a biphosphorylated derivative in which one Thr and one Ser are phosphorylated at positions 231 and 235 respectively and which are recognized by an Alzheimer's disease-specific monoclonal antibody has been carried out. Mutant peptides with Tyr substitutions preceding the Pro residues have been synthesized. It was found that phosphorylation of Tyr seems to have an effect on the equilibrium ratio of cis-transisomerization and lowers the cis content. Phosphorylation in conformation of Tau peptides may have a role in Alzheimer's disease.

The chemical synthesis and folding of the macrocyclic peptide kalata B1 are described using two approaches. The first involved the oxidation of the cysteine residues of a linear precursor protein to form the correct disulfide bonds that led to the folding of the three-dimensional structure. The second involved cyclization prior to oxidation. Results demonstrate that cyclization has a major effect on the folding pathway and facilitates formation of the correctly disulfide-bonded form in aqueous solution.

The overall structures of the first and the second repeats of the receptor binding domains of human low-density lipoprotein receptor rLB1 and rLB2 are similar. The beta-hairpin is the largest single element in the secondary structure of both. But there are two additional residues between cysteine 12 and cysteine 19 in rLB2 which increase the distance between the two strands. This results in the loss of interstrand hydrogen bonds. The rLB2 aqueous solution structure is resolved by two-dimensional hydrogen NMR spectroscopy.

Amino-terminal ligand-binding (LB) repeat of the human low density lipoprotein receptor is expressed as a recombinant peptide in order to analyze the disulfide-bonding pattern, and the structure and function of LB repeats. Disulfide bond connections are made in two ways. In the first way, amino acids produced from the digestion of nonspecific proteolytic enzyme proteinase K contains single disulfide bond connecting Cys(IV) and Cys(VI). In the other approach, reduction of disulfide bonds occurs.

The three dimensional structure of a cysteine-rich repeat from the low-density lipoprotein (LDL) receptor has been evaluated by two-dimensional NMR spectroscopy, which shows that it has a beta-hairpin structure and a series of beta turns. LDL receptors play a central role in mammalian cholesterol metabolism by clearing lipoproteins which bear apolipoproteins E and B-100 from plasma. Mutations in this receptor are related to familial hypercholesterolemia.

The application of selenocysteine in a supported phase method to direct native folding and produce [alpha]-conotoxins efficiently with improved biophysical properties is reported. The results obtained provide insight into the development of more stable and potent nicotinic antagonists suitable for new drug therapies, and highlight the application of selenocysteine technology more broadly to disulfide-bonded peptides and proteins.

The tertiary structure of retrocyclin-2 is determined in a membrane-mimicking environment and a well-defined [beta]-hairpin structure is present in the presence of SDS micelles. The ability to self-associate has contributed to the high-affinity binding of retrocyclins for glycoproteins by increasing the valency and increasing the ability of retrocyclins to cross-link cell surface glycoproteins.

The three-dimensional structure determined using (super 1)H NMR spectroscopy is presented and the potent insecticidal activity for one of these peptides, kalata B2 is demonstrated. Examination of the sequence reveals that they could be separated in to two subfamilies, one of which contains a larger number of positively charged residues and has a bracelet-like circularization of the backbone, and the other contains a backbone twist due to a cis-peptidyl-proline bond and might conceptually be regarded as a molecular Mobius strip.

Research has been conducted on amino acid bacterial peptide microcin J25. The authors have discovered that this peptide does not have a head-to-tail cyclic structure but possesses side chain to backbone cyclization.

Research has been conducted on circular backbone protein which is responsible for cyclotide stability. The role of this protein in determining the structure and biological activity of cyclotides has been investigated via the synthesis and characterization of an acyclic derivative, and the results are reported.