Characterization of ConantokinRl-A: Molecular Phylogeny as Structure/Function Study

A multidisciplinary strategy for discovery of new Conus venom peptides combines molecular genetics and phylogenetics with peptide chemistry and neuropharmacology. Here we describe application of this approach to the conantokin family of conopeptides targeting NMDA receptors. A new conantokin from Conus rolani , Con Rl -A, was identified using molecular phylogeny and subsequently synthesized and functionally characterized. Con Rl -A is a 24-residue peptide containing three gamma-carboxyglutamic acid residues with a number of unique sequence features compared to conantokins previously characterized. The HPLC elution of Con Rl -A suggested that this peptide exists as two distinct, slowly exchanging conformers. Con Rl -A is predominantly helical (estimated helicity of 50%), both in the presence and absence of Ca ++ . The order of potency for blocking the four NMDA receptor subtypes by Con Rl -A was NR2B>NR2D>NR2A>NR2C. This peptide has a greater discrimination between NR2B and NR2C then any other ligand reported so far. In summary, Con Rl -A is a new member of the conantokin family that expands our understanding of structure/function of this group of peptidic ligands targeted to NMDA receptors. Thus, incorporating phylogeny in the discovery of novel ligands for the given family of ion channels or receptors is an efficient means of exploring the megadiverse group of peptides from genus Conus .