Expression and characterization of the antimicrobial peptide gambicin from culex quinquefasciatus

Abstract

Antimicrobial peptides (AMPs), which can be found in many organisms, are generally low molecular weight peptides containing less than 100 amino acid residues. Due to ineffective conventional antibiotic treatments causing numerous mortalities of infected patients in the world, AMPs are an interesting approach to the development of novel therapeutics against pathogens, particularly antibioticresistant bacteria, because they are safe, non-toxic to mammals, no bacterial resistance and showing broadspectrum antimicrobial activity. Interestingly, an antimicrobial peptide gambicin isolated from An. gambiae cell lines possess antimicrobial activity against gram-positive and -negative bacteria, filamentous fungi, and Plasmodium species. However, the isolation of Culex gambicin and expression of recombinant mosquito gambicins remain unreported. This study aimed to express recombinant Culex gambicin in Pichia pastoris and/ or baculovirus expression system, and successfully cloned and expressed. SDS-PAGE of Culex gambicin in Pichia pastoris revealed an obvious protein band with a molecular weight of 7.0 kDa, indicating high production of recombinant Culex gambicin. Testing of antimicrobial activity against E. coli DH5a strain by agar-well diffusion assay exhibited no activity. A refolding approach to the recovery of antimicrobial peptides is required for further studies, while the expression of recombinant gambicin in the baculovirus expression system is on the process which will be also discussed.