Isolation and characterisation of a new antimicrobial peptide from the skin of Xenopus laevis

A new antimicrobial peptide (AMP) named PGLa-H has been isolated from the skin of the African clawed frog (Xenopus laevis) using gel filtration and reverse-phase high-performance liquid chromatography (RP-HPLC). Its amino acid sequence was determined as KIAKVALKAL by Edman degradation, with a molecular weight of 1053.727 Da as analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). No similar AMP was found by BLAST search. Purified PGLa-H demonstrated antimicrobial ability against the reference bacteria Escherichia coli ATCC 25922 [minimum inhibitory concentration (MIC) = 23.6 μg/mL], Staphylococcus aureus ATCC 25923 (MIC = 8.7 μg/mL) and Bacillus subtilis (MIC = 14.4 μg/mL) and was active against multidrug-resistant meticillin-resistant S. aureus (MRSA) (MIC = 67.8 μg/mL). The antimicrobial mechanism for this new peptide was further investigated by transmission electron microscopy. PGLa-H killed cells by destroying the cell membrane.