title: Muscarinic toxin-like proteins from Taiwan banded krait (Bungarus multicinctus) venom: purification, characterization and gene organization.
abstract: Two novel proteins, BM8 and BM14, were isolated from Bungarus multicinctus (Taiwan banded krait) venom using the combination of chromatography on a SP-Sephadex C-25 column and a reverse-phase HPLC column. Both proteins contained 82 amino acid residues including 10 cysteine residues, but there were two amino acid substitutions at positions 37 and 38 (Glu37-Ala38 in BM8; Lys37-Lys38 in BM14). CD spectra and acrylamide quenching studies revealed that the gross conformation of BM8 and BM14 differed. In contrast to BM8, BM14 inhibited the binding of [3H]quinuclidinyl benzilate to the M2 muscarinic acetylcholine (mAchR) receptor subtype. Trinitrophenylation of Lys residues abolished the mAchR-binding activity of BM14, indicating that the Lys substitutions at positions 37 and 38 played a crucial role in the activity of BM14. The genomic DNA encoding the precursor of BM14 was amplified by PCR. The gene shared virtually identical structural organization with alpha-neurotoxin and cardiotoxin genes. The intron sequences of these genes shared a sequence identity up to 84%, but the protein-coding regions were highly variable. These results suggest that BM8, BM14, neurotoxins and cardiotoxins may have originated from a common ancestor, and the evolution of snake venom proteins shows a tendency to diversify their functions.
authors.affiliation: Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung, Taiwan.
authors.forename: Charling
authors.initials: C
authors.lastname: Chung
authors.forename: Bin-Nan
authors.initials: BN
authors.lastname: Wu
authors.forename: Chen-Chung
authors.initials: CC
authors.lastname: Yang
authors.forename: Long-Sen
authors.initials: LS
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002038:Bungarotoxins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D017838:Bungarus / Q000235:genetics* / Q000378:metabolism; D002850:Chromatography, Gel; D004247:DNA / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011813:Quinuclidinyl Benzilate / Q000037:antagonists & inhibitors / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D002038:Bungarotoxins; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate; D004247:DNA