Structural and functional characterization of myotoxin I, a Lys49 phospholipase A2 homologue from the venom of the snake Bothrops atrox.
A new myotoxin was isolated from the venom of Bothrops atrox from Colombia. B. atrox myotoxin I is a homodimer, with a subunit molecular mass of 13,826, and a pI of 8.9. Its complete nucleotide sequence was obtained by cDNA cloning, indicating a mature product of 122 residues that belongs to the family of Lys49 phospholipase A(2) (PLA(2)) homologues, a subgroup of catalytically inactive proteins within the group IIA. Accordingly, the toxin was devoid of phospholipase and anticoagulant activities, in vitro. In mice, it induced conspicuous local myonecrosis, edema, and a systemic interleukin-6 response. In vitro, it was cytolytic upon myoblasts, and weakly bactericidal. The toxin showed highest homology with other Lys49 PLA(2)s, both in its primary and three-dimensional modeled structure, although with an evident difference in the C-terminal region. Unlike Lys49 proteins of American crotalids having 121 residues, this toxin presents an insertion (Asn) between positions 118 and 119. Despite several substitutions within the C-terminal region 115-129 between B. atrox myotoxin I and B. asper myotoxin II, antibodies against synthetic peptide 115-129 of the latter were strongly cross-reactive to the former, indicating the antigenic conservation of this site, known to be critical for the membrane-damaging activities of Lys49 myotoxins.
Núñez
Vitelbina
V
Programa de Ofidismo, Facultad de Medicina, Universidad de Antioquia, A.A. 1226, Medellin, Colombia.
Arce
Viviana
V
Gutiérrez
José María
JM
Lomonte
Bruno
B
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001483:Base Sequence; D017837:Bothrops; D003429:Cross Reactions / Q000276:immunology; D003435:Crotalid Venoms / Q000737:chemistry*; D018076:DNA, Complementary / Q000235:genetics; D004487:Edema / Q000139:chemically induced; D004591:Electrophoresis, Polyacrylamide Gel; D054501:Group II Phospholipases A2; D007124:Immunoenzyme Techniques; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology; D032446:Myoblasts / Q000187:drug effects; D009336:Necrosis; D009498:Neurotoxins / Q000737:chemistry* / Q000235:genetics* / Q000633:toxicity; D010741:Phospholipases A / Q000737:chemistry* / Q000235:genetics* / Q000633:toxicity; D054467:Phospholipases A2; D011487:Protein Conformation; D030162:Reptilian Proteins; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D000906:Antibodies; D003435:Crotalid Venoms; D018076:DNA, Complementary; D015850:Interleukin-6; D009498:Neurotoxins; D030162:Reptilian Proteins; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2; C076780:myotoxin I