Binds to the lipid A moiety of bacterial lipopolysaccharides (LPS), a glycolipid present in the outer membrane of all Gram-negative bacteria. Shows a potent antimicrobial activity against the Gram-negative bacteria E.coli, S.typhimurium and P.aeruginosa. Less active against the Gram-positive bacteria S.aureus, L.monocytogenes and B.subtilis. BAC5 sequence consists almost exclusively of X-P-P-Y repeats. Elastase is responsible for its maturation. Belongs to the cathelicidin family.