Mastoparan B, a cationic toxin, is the major peptide component in the venom of Vespa basalis. Molecular cloning of its cDNA fragment revealed that this toxin was initially synthesized as a precursor polypeptide, containing an N-terminal signal sequence, a prosequence, the mature toxin, and an appendix glycine at C-terminus. Sequence alignment between precursors of mastoparan B and melittin from honeybee venom showed a significant conservation in prosequence. Alternate positions existing in both prosequences were either proline or alanine known as the potential cleaving sites for dipeptidyl peptidase IV. Subsequently, a putative dipeptidyl peptidase IV cDNA fragment was cloned from Vespa basalis venom gland. The prosequence may possibly be removed via sequential liberation of dipeptides during the processing of mastoparan B.

Mastoparan B is a cationic, amphiphilic tetradecapeptide toxin isolated from the venom of the black-bellied hornet (Vespa basalis), the most dangerous species of wasps found in Taiwan. Mastoparan B was evaluate possess antibacterial activity and cardiovascular depress activity. However, mastoparan B is low abundance in the venom (3.4% of crude venom). In this study, mastoparan B was overexpressed in Escherichia coli BL21 as a recombinant protein fused the C-terminus of oleosin by a linker polypeptide, intein S. Artifical oil bodies (AOBs) were reconstituted with triacylglycerol, phospholipid to obtain the insoluble recombinant protein. Mastoparan B was subsequently released through self-splicing of intein induced by temperature alteration from artifical oli bodies, and the recombinant mastoparan B was collected it in the supernatant after centrifugation. Recombinant mastoparan B release from AOBs was exhibited membrane permeabilization activity, bacteriostatic and bactericidal activity. These results have shown that mastoparan B was successfully expressed and purified via the efficient AOB expression/purification system.