A bactericidal homodimeric phospholipases A2 from Bungarus fasciatus venom

Group IIA secretory phospholipases A2 (sPLA2-II) is generally known to display potent gram-positive bactericidal activity, while group IA sPLA2 (sPLA2-I) reportedly is not. In this work, a novel sPLA2-I named BFPA was identified from Bungarus fasciatus venom, and its antimicrobial activity was studied as well. The amino acid sequence of the venomous protein precursor was 145-amino acid in length, and contained a predicted 27-amino acid signal peptide and a 118-amino acid mature protein. Unlike the well-known sPLA2-Is, which have 14 half-cysteines forming 7 intramolecular disulfide bridges, BFPA possesses 15 half-cysteines. The additional cysteine might contribute to the formation of an intermolecular disulfide bridge of the homodimeric protein. In the biological activities assays, BFPA displayed the activities of anticoagulation and bactericidal against Escherichia coli and Staphylococcus aureus. This study is the first report about gram-positive bactericidal activity of sPLA2-I.