title: Role of modified glutamic acid in the helical structure of conantokin-T.
abstract: Circular dichroism (CD) and 2-dimensional NMR were used to study the solution conformation of conantokin-T (Con-T), a small peptide toxin found in the venom of fish-hunting cone snails, and its Glu-substituted analog. Con-T lacks disulfide bonds but contains many gamma-carboxyglutamic acids (Gla), a post-translationally modified residue. Our results show that Con-T adopts an alpha-helical conformation in aqueous solution even in the absence of calcium. Glu replacements diminish both helicity and function of Con-T. The helical content of Con-T is higher than most natural helical peptides of this length in aqueous solution. The sequence of this small toxin incorporates several known elements that stabilize alpha-helical structure in peptides. Gla residues form several salt bridges that stabilize helical conformation of Con-T.
authors.affiliation: Department of Life Sciences, National Tsing Hua University, Hsin-chu, Taiwan.
authors.forename: C H
authors.initials: CH
authors.lastname: Lin
authors.forename: C S
authors.initials: CS
authors.lastname: Chen
authors.forename: K S
authors.initials: KS
authors.lastname: Hsu
authors.forename: D S
authors.initials: DS
authors.lastname: King
authors.forename: P C
authors.initials: PC
authors.lastname: Lyu
mesh_terms: D015055:1-Carboxyglutamic Acid / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D020916:Conotoxins; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry* / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000737:chemistry* / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D017433:Protein Structure, Secondary; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects
chemical_list: D020916:Conotoxins; D018691:Excitatory Amino Acid Antagonists; D036341:Intercellular Signaling Peptides and Proteins; D008978:Mollusk Venoms; D010455:Peptides; D010456:Peptides, Cyclic; D016194:Receptors, N-Methyl-D-Aspartate; C106241:conantokin ET; C063571:conantokin-T; D015055:1-Carboxyglutamic Acid