Host defense peptide that exhibits antimicrobial activity against both Gram-negative bacteria, such as E.coli and S.typhimurium, and Gram-positive bacteria, such as S.aureus and B.subtilis (PubMed:15033915, PubMed:33224970). Inhibits cell adhesion of E.coli on intestinal epithelial enterocytes (PubMed:33224970). Causes rapid permeabilization of both the outer and inner membrane of E.coli, leading to morphological alterations on the bacterial surface (PubMed:15033915). Binds to bacterial lipopolysaccharides (LPS) with high affinity, and may thereby be involved in immunoregulation through LPS neutralization (PubMed:33181266). May contribute to epididymal innate immunity and protect the sperm against attack by microorganisms (PubMed:15033915). High-level and epididymis-specific expression (PubMed:12600824). Most abundant in the epithelium of the caput and present in the epididymis lumen and bound to sperm (PubMed:12600824). Also expressed in pancreas (PubMed:12600824). The three-dimensional structure formed by the three intramolecular disulfide bridges is indispensable for antimicrobial activity. Belongs to the beta-defensin family.