Defensin beta 118

Also known as: Beta-defensin 18, Epididymal secretory protein 13.6, DEFB118, Q96PH6

Defensin beta 118 (DEFB118), also known as beta-defensin 18 or epididymal secretory protein 13.6, is a host defense peptide primarily expressed in the male reproductive tract. Its mechanism of action involves direct antimicrobial activity against a broad spectrum of bacteria, including Gram-negative species such as *Escherichia coli* and *Salmonella typhimurium*, as well as Gram-positive species like *Staphylococcus aureus* and *Bacillus subtilis*. This activity is mediated by electrostatic interactions with bacterial membranes, leading to membrane disruption and cell death, a common feature of defensin family peptides. As of the current research status, DEFB118 remains at an experimental stage with no published PubMed references available. Key findings are limited to preliminary characterization of its antimicrobial spectrum and tissue-specific expression, suggesting a potential role in protecting the epididymis and spermatozoa from microbial infection. However, detailed mechanistic studies, in vivo efficacy data, and structural analyses are lacking. Clinical relevance is speculative at this point. Given its localized expression and antimicrobial properties, DEFB118 could theoretically be explored as a therapeutic agent for male reproductive tract infections or as a template for novel antibiotic design. However, without peer-reviewed research or clinical trials, its translational potential remains unsubstantiated. For research purposes only — not medical advice.

Key data

Mechanism of action

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)

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