title: Proton NMR assignments and secondary structure of the snake venom protein echistatin.
abstract: The snake venom protein echistatin is a potent inhibitor of platelet aggregation. The inhibitory properties of echistatin have been attributed to the Arg-Gly-Asp sequence at residues 24-26. In this paper, sequence-specific nuclear magnetic resonance assignments are presented for the proton resonances of echistatin in water. The single-chain protein contains 49 amino acids and 4 cystine bridges. All of the backbone amide, C alpha H, and side-chain resonances, except for the eta-NH of the arginines, have been assigned. The secondary structure of the protein was characterized from the pattern of nuclear Overhauser enhancements, from the identification of slowly exchanging amide protons, from 3JC alpha H-NH coupling constants, and from circular dichroism studies. The data suggest that the secondary structure consists of a type I beta-turn, a short beta-hairpin, and a short, irregular, antiparallel beta-sheet and that the Arg-Gly-Asp sequence is in a flexible loop connecting two strands of the distorted antiparallel beta-sheet.
authors.affiliation: Chemistry Department, Rutgers University, Piscataway, New Jersey 08854.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: S M
authors.initials: SM
authors.lastname: Pitzenberger
authors.forename: V M
authors.initials: VM
authors.lastname: Garsky
authors.forename: P K
authors.initials: PK
authors.lastname: Lumma
authors.forename: G
authors.initials: G
authors.lastname: Sanyal
authors.forename: J
authors.initials: J
authors.lastname: Baum
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D036341:Intercellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010455:Peptides; D011487:Protein Conformation; D011522:Protons; D013056:Spectrophotometry, Ultraviolet; D014757:Viper Venoms / Q000737:chemistry*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011522:Protons; D014757:Viper Venoms; C057986:echistatin