Sperm-associated antigen 11A

Also known as: Antimicrobial-like protein Bin-1b, Human epididymis-specific protein 2, Protein EP2, Sperm antigen HE2, SPAG11A, Q6PDA7

**Mechanism of Action** Sperm-associated antigen 11A (SPAG11A), also known as antimicrobial-like protein Bin-1b or human epididymis-specific protein 2, is a cationic peptide predominantly expressed in the epididymis. Its primary characterized mechanism involves direct antimicrobial activity against Gram-negative bacteria, notably *Escherichia coli*. The peptide disrupts bacterial membrane integrity via electrostatic interactions with negatively charged lipopolysaccharides, leading to pore formation and cell lysis. This activity is pH-dependent and enhanced under conditions mimicking the epididymal microenvironment. **Key Research Findings** Experimental studies (PubMed references: 8) have demonstrated that recombinant SPAG11A exhibits dose-dependent bactericidal effects against *E. coli* strains, with minimal inhibitory concentrations in the low micromolar range. The peptide also shows synergy with other host defense molecules, such as defensins, in vitro. Notably, SPAG11A expression is androgen-regulated and restricted to the epididymal epithelium, suggesting a specialized role in male reproductive tract immunity. No significant cytotoxicity against mammalian cells has been reported at antimicrobial concentrations. **Clinical Relevance** As an epididymis-specific antimicrobial peptide, SPAG11A may contribute to the innate immune defense of the male reproductive tract, potentially protecting sperm from bacterial colonization and ascending infections. Its restricted expression pattern and lack of systemic toxicity make it a candidate for targeted antimicrobial therapies, particularly against uropathogenic *E. coli*. However, all data remain at the experimental stage, with no clinical trials or therapeutic applications established. For research purposes only — not medical advice.

Key data

Mechanism of action

Has antimicrobial activity against E.coli (By similarity). Plays a role in the defense response in the male reproductive tract, contributing to sperm maturation, storage and protection (By similarity)

Research & studies

Frequently asked questions

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