Ohanin - A novel protein from king cobra (Ophiophagus hannah) venom

Abstract

We describe the identification, purification, and structural and functional characterization of the first member of a new family of snake venom proteins. The novel protein, named ohanin, was identified by LC/MS, purified by a two-step chromatography, and sequenced using Edman degradation sequencing. It shows 44 % identity to PRY-SPRY domains of B30.2 domain-containing proteins. Ohanin lowers the locomotor activity and induces hyperalgesia in mice when administered by both intraperitoneal and intracerebroventricular routes. Both these pharmacological effects are mediated through its effect on the central nervous system. As ohanin is found in low abundance in king cobra venom, we have designed and constructed a synthetic gene for ohanin. The recombinant protein expressed in E. coli is structurally and functionally similar to the native protein. In addition, we have also cloned and sequenced the cDNA for ohanin. Its full-length cDNA sequence of 1558 bp encodes for prepro-ohanin with a propeptide segment at the C-terminal. Recombinant pro-ohanin shows potent effect on locomotion when injected i. c. v. but not when injected i. p. Thus maturation appears to be crucial for the biological activity of ohanin. The genomic DNA sequencing indicates the presence of five exons and four introns. Interestingly, the second exon encoding the 5a??-untranslated region is alternatively spliced. All these findings together indicate that ohanin forms a new subfamily of B30.2 domain-containing proteins.