A defensin-like antimicrobial peptide from the venoms of spider, Ornithoctonus hainana.

The defensin-like antimicrobial peptides have been characterized from various other arthropods including insects, scorpions, and ticks. But no natural spider defensin-like antimicrobial peptides have ever been isolated from spiders, except couple of cDNA and DNA sequences of five spider species revealed by previous genomic study. In this work, a defensin-like antimicrobial peptide named Oh-defensin was purified and characterized from the venoms of the spider, Ornithoctonus hainana. Oh-defensin is composed of 52 amino acid (aa) residues including six Cys residues that possibly form three disulfide bridges. Its aa sequence is MLCKLSMFGAVLGV PACAIDCLPMGKTGGSCEGGVCGCRKLTFKILWDKKFG. By BLAST search, Oh-defensin showed significant sequence similarity to other arthropod antimicrobial peptides of the defensin family. Oh-defensin exerted potent antimicrobial activities against tested microorganisms including Gram-positive bacteria, Gram-negative bacteria, and fungi. The cDNA encoding Oh-defensin precursor was also cloned from the cDNA library of O. hainana.