Alanine scanning analysis of the antimicrobial peptide lyp1987 using a template-based approach

A preference for several amino acids is observed to occur at particular positions of cationic -helical antimicrobial peptides (AMPs), which ensures the formation of amphipathic regions once they assume their correct secondary structure in membranes or membrane-mimicking environments and makes them active against pathogens.This study determined the effect of alanine mutations on the secondary structure and bioactivity of lyp1987 (GRLQAFLAKMKEIAAQTL-NH 2 ), a cationic -helical AMP obtained from the venom of Lycosa poonaensis which exhibits broad range activity against Gram-positive and Gram-negative bacteria with micromolar minimum inhibitory concentrations (MIC).CD spectroscopy revealed no significant difference in the secondary structure, with all alanine-substituted analogs exhibiting predominantly -helical structure in buffered 2,2,2trifluoroethanol solution.Alanine substitution at Glu12 and Thr17 increased the activity of lyp1987 against Gram-positive andnegative bacteria, while alanine substitution at Lys9 increased its selectivity against Gram-positive bacteria.Further investigation can be done to determine positions and substitutions that will give less cytotoxic analogs.