title: Sequence-specific 1H-NMR assignments and determination of the secondary structure in aqueous solution of the cardiotoxins CTXIIa and CTXIIb from Naja mossambica mossambica.
abstract: Sequence-specific assignments of the 1H-nuclear magnetic resonance (NMR) spectra of the cardiotoxins CTXIIa and CTXIIb from Naja mossambica mossambica were obtained using two-dimensional NMR experiments at 500 MHz and the independently determined amino acid sequences. Assignments were obtained from data at 25 degrees C and 45 degrees C for all but one backbone proton of the 60 residues in each protein. Complete or partial assignments are also reported for the side-chain protons. These assignments supercede those published previously for the toxin preparation VII2 [Hosur, R. V., Wider, G. & Wüthrich K. (1983) Eur. J. Biochem. 130, 497-508]. The 1H/2H-exchange kinetics were measured in 2H2O at 20 degrees C for the amide protons and the N-terminal amino group. These and additional NMR data enabled the determination of the secondary structure in aqueous solution, which is virtually identical in CTXIIa and CTXIIb. Both proteins contain a short double-stranded antiparallel beta-sheet comprising the residues 2-4 and 11-13, and a triple-stranded antiparallel beta-sheet consisting of the residues 20-26, 35-39, and 49-55. The two peripheral strands of the triple-stranded beta-structure were found to be connected by a right-handed cross-over, and the locations of several tight turns were also identified.
authors.affiliation: Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Otting
authors.forename: W E
authors.initials: WE
authors.lastname: Steinmetz
authors.forename: P E
authors.initials: PE
authors.lastname: Bougis
authors.forename: H
authors.initials: H
authors.lastname: Rochat
authors.forename: K
authors.initials: K
authors.lastname: Wüthrich
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D004735:Energy Transfer; D006321:Heart / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D011506:Proteins / Q000302:isolation & purification*; D011522:Protons; D012910:Snake Venoms / Q000032:analysis*
chemical_list: D000596:Amino Acids; D011506:Proteins; D011522:Protons; D012910:Snake Venoms