A phospholipase A2-like pseudogene retaining the highly conserved introns of Mojave toxin and other snake venom group II PLA2s, but having different exons.
Mojave toxin is a neurotoxic, heterodimeric phospholipase A2 (PLA2) from the venom of the Mojave rattlesnake (Crotalus scutulatus scutulatus) and is characteristic of all rattlesnake presynaptic neurotoxins. Here, we describe a phospholipase A2 pseudogene (psi-Mtx) located 2,000 nucleotides upstream, and on the opposite DNA strand, from a gene for Mojave toxin acidic subunit (Mtx-a). The pseudogene lacks the first exon and a few segments of noncoding DNA found in functional snake venom PLA2 genes, but does have the coding information for a complete PLA2 protein. psi-Mtx retains the unusual gene sequence similarity pattern found in functional viperid PLA2 genes. When compared to genes from C. s. scutulatus and the Hahn snake (Trimeresurus flavoviridus), psi-Mtx shows strong conservation of nocoding regions and variable protein-coding regions. Although the nocoding regions of psi-Mtx are conserved with respect to other viperid PLA2 genes, the three exons code for a unique PLA2-like protein similar in sequence to ammodytoxin b found in the venom of the western sand viper (Vipera ammodytes ammodytes). The structure of these genes suggests a common ancestor for all viperid PLA2 genes. Phylogenetic analysis of psi-Mtx, Mtx-a, Mtx-b, pgPLA 1a, and pgPLA 1b suggest that psi-Mtx diverged from an ancestral sequence before the presumed gene duplication event leading to Mtx-a and Mtx-b. However, analysis of the basis of coding regions alone gives a conflicting result.
John
T R
TR
University of Wyoming, Department of Molecular Biology, Laramie 82071-3944, USA.
Smith
J J
JJ
Kaiser
I I
II
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D003435:Crotalid Venoms / Q000235:genetics*; D017839:Crotalus / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000235:genetics*; D010741:Phospholipases A / Q000235:genetics*; D054467:Phospholipases A2; D010802:Phylogeny; D011544:Pseudogenes / Q000235:genetics*; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D017819:Viperidae / Q000235:genetics
D003435:Crotalid Venoms; C018107:Mojave toxin; D009498:Neurotoxins; D010741:Phospholipases A; D054467:Phospholipases A2