title: Structural studies of alpha-bungarotoxin. 3. Corrections in the primary sequence and X-ray structure and characterization of an isotoxic alpha-bungarotoxin.
abstract: The most plausible set of chemical shift assignments for alpha-bungarotoxin as deduced from the combined use of two-dimensional J-correlated and two-dimensional nuclear Overhauser effect 1H nuclear magnetic resonance (NMR) spectroscopy was in conflict with the accepted amino acid sequence between residues 8 and 12 and residues 66 and 70 [Basus, V. J., Billeter, M., Love, R. A., Stroud, R. M., & Kuntz, I. D. (1988) Biochemistry (first paper of three in this issue]). Furthermore, NMR spectra of alpha-bungarotoxin, purified by conventional methods, evidenced a second species at the level of approximately 10% total protein. The minor component was separated from alpha-bungarotoxin by Mono-S (cationic) chromatography. Sequencing of Mono-S-purified alpha-bungarotoxin and one of its tryptic peptides showed that the correct sequence for alpha-bungarotoxin is Ser-Pro-Ile at positions 9-11 and Pro-His-Pro at positions 67-69. The electron density map of alpha-bungarotoxin [Love, R. A., & Stroud, R. M. (1986) Protein Eng. 1, 37] was refined with the new sequence data. Improvements in the structure were found primarily for residues 9-11. Sequence analysis of two overlapping tryptic peptides proved that the minor species differed from alpha-bungarotoxin by replacement of a valine for an alanine at position 31. This new toxin, alpha-bungarotoxin(Val-31), binds to the acetylcholine receptor with an affinity that is comparable to that of alpha-bungarotoxin.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco 94143.
authors.forename: P A
authors.initials: PA
authors.lastname: Kosen
authors.forename: J
authors.initials: J
authors.lastname: Finer-Moore
authors.forename: M P
authors.initials: MP
authors.lastname: McCarthy
authors.forename: V J
authors.initials: VJ
authors.lastname: Basus
mesh_terms: D000595:Amino Acid Sequence; D002038:Bungarotoxins; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D002038:Bungarotoxins