Molecular cloning and functional identification of analgesic peptides from Buthus martensii Karsch

Aim: To clone genes encoding analgesic peptides from the cDNA pool of scorpion telson, to obtain recombinant peptides by prokaryotic expression system and examine their analgesic activity in mouse twisting test. Material and methods: The genes encoding analgesic peptides were cloned from the cDNA pool of scorpion telson by nested PCR. Positive clones were sequenced after screened by PCR-SSCP. The recombinant peptides were obtained by functionally expression in E. coli and purified by metal chelating chromatography. The bioactivity was assayed in mouse twisting test. Results: Two nucleotide sequences encoding potential analgesic peptides were obtained. They were named as BmK 22 and BmK 9. BmK 22 was a new peptide with only one amino acid at site 54 different with BmK 9. In mouse-twisting test, both of the two recombinant peptides exhibited analgesic activity, and BmK 9 showed a stronger activity in pain relieving. Further, when considering structure factors by homology modeling, we speculated that the Arg residue at site 54 of BmK 9 may play an important role in target recognition and influence the analgesic activity. Conclusion: Venoms from scorpions contain extremely rich bioactive peptides. The strategy in this paper involving molecular cloning, functional expression and bioactivity identification of BmK 9 and BmK 22 provided a rapid route to discover scorpion toxins with special bioactivity such as analgesics.