title: Amino acid sequence of fibrolase, a direct-acting fibrinolytic enzyme from Agkistrodon contortrix contortrix venom.
abstract: The complete amino acid sequence of fibrolase, a fibrinolytic enzyme from southern copperhead (Agkistrodon contortrix contortrix) venom, has been determined. This is the first report of the sequence of a direct-acting, nonhemorrhagic fibrinolytic enzyme found in snake venom. The majority of the sequence was established by automated Edman degradation of overlapping peptides generated by a variety of selective cleavage procedures. The amino-terminus is blocked by a cyclized glutamine (pyroglutamic acid) residue, and the sequence of this region of the molecule was determined by mass spectrometry. Fibrolase is composed of 203 residues in a single polypeptide chain with a molecular weight of 22,891, as determined by the sequence. Its sequence is homologous to the sequence of the hemorrhagic toxin Ht-d of Crotalus atrox venom and with the sequences of two metalloproteinases from Trimeresurus flavoviridis venom. Microheterogeneity in the sequence was found at both the amino-terminus and at residues 189 and 192. All six cysteine residues in fibrolase are involved in disulfide bonds. A disulfide bond between cysteine-118 and cysteine-198 has been established and bonds between cysteines-158/165 and between cysteines-160/192 are inferred from the homology to Ht-d. Secondary structure prediction reveals a very low percentage of alpha-helix (4%), but much greater beta-structure (39.5%). Analysis of the sequence reveals the absence of asparagine-linked glycosylation sites defined by the consensus sequence: asparagine-X-serine/threonine.
authors.affiliation: Chiron Research Laboratories, Chiron Corporation, Emeryville, California 94608.
authors.forename: A
authors.initials: A
authors.lastname: Randolph
authors.forename: S H
authors.initials: SH
authors.lastname: Chamberlain
authors.forename: H L
authors.initials: HL
authors.lastname: Chu
authors.forename: A D
authors.initials: AD
authors.lastname: Retzios
authors.forename: F S
authors.initials: FS
authors.lastname: Markland
authors.forename: F R
authors.initials: FR
authors.lastname: Masiarz
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D003435:Crotalid Venoms / Q000201:enzymology*; D003488:Cyanogen Bromide; D010450:Endopeptidases / Q000378:metabolism; D014644:Genetic Variation; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D012911:Snakes
chemical_list: C031442:Agkistrodon venoms; D000596:Amino Acids; D003435:Crotalid Venoms; D010455:Peptides; D010450:Endopeptidases; D008666:Metalloendopeptidases; C058789:fibrolase; D003488:Cyanogen Bromide