The crystal structure of the calcium-bound con-G[Q6A] peptide reveals a novel metal-dependent helical trimer.

The ability to form and control both secondary structure and oligomerization in short peptides has proven to be challenging owing to the structural instability of such peptides. The conantokin peptides are a family of γ-carboxyglutamic acid containing peptides produced in the venoms of predatory sea snails of the Conus family. They are examples of short peptides that form stable helical structures, especially in the presence of divalent cations.

Metal ion determinants of conantokin dimerization as revealed in the X-ray crystallographic structure of the Cd(2+)/Mg (2+)-con-T[K7gamma] complex.

Predatory sea snails from the Conus family produce a variety of venomous small helical peptides called conantokins that are rich in gamma-carboxyglutamic acid (Gla) residues. As potent and selective antagonists of the N-methyl-D: -aspartate receptor, these peptides are potential therapeutic agents for a variety of neurological conditions. The two most studied members of this family of peptides are con-G and con-T.

The crystal structures of the calcium-bound con-G and con-T[K7gamma] dimeric peptides demonstrate a metal-dependent helix-forming motif.

Short peptides that have the ability to form stable alpha-helices in solution are rare, and a number of strategies have been used to produce them, including the use of metal chelation to stabilize folding of the backbone. However, no example exists of a structurally well-defined helix stabilized exclusively through metal ion chelation. Conantokins (con)-G and -T are short peptides that are potent antagonists of N-methyl-D-aspartate receptor channels.

X-ray crystallographic structure of the angiogenesis inhibitor, angiostatin, bound to a peptide from the group A streptococcal surface protein PAM.

The crystal structure of the human Pg-derived angiogenesis inhibitor, angiostatin, complexed to VEK-30, a peptide from the group A streptococcal surface protein, PAM, was determined and refined to 2.3 A resolution. This is the first structure of angiostatin bound to a ligand and provides a model of the interaction between Pg and streptococcal-derived pathogenic proteins.