Antimicrobial peptide. Active against a broad spectrum of Gram-positive and Gram-negative bacteria including methicillin-resistant S.aureus ATCC 43 300, S.aureus BAA-39, pathogenic strains of L.monocytogenes, K.pneumoniae, E.coli O157:H7, S.typhimurium and multidrug-resistant S.typhimurium DT104 with minimum inhibitory concentration (MIC) of 1.4 uM for all except for S.aureus BAA-39 (PubMed:18265434). Also active against Serratia marcescens (PubMed:14728663). Probably acts by disturbing membrane functions with its amphipathic alpha-helical structure (PubMed:18265434). May protect a developing embryo from bacterial infection (Probable). Monomer. Expressed at low levels in nerve tissue, salivary gland, Malpighian tubule, trachea, midgut, fat body, integument and muscle from day 3, fifth instar naive larvae. Moderate levels expressed in fat body from the 4th instar larvae (day 0), 5th instar larvae (days 3 and 6), wandering larvae (day 6), and adults in the absence of infection. A moderate level of expression in the hemocytes of the naive larvae. Expression increases substantially in fat body and hemocytes after fifth instar larvae are challenged with bacterial cells (PubMed:18265434). Constitutive low expression in naive eggs, but up-regulated in them in response to bacteria. Expressed in 24 h (predorsal closure stage) eggs in extra-embryonic tissues (yolk and serosa) after bacterial challenge, but not in embryos (PubMed:14728663). By bacterial infection. Belongs to the moricin family.