Antibacterial properties of the sperm-binding proteins and peptides of human epididymis 2 (HE2) family; salt sensitivity, structural dependence and their interaction with outer and cytoplasmic membranes of Escherichia coli.
During passage through the epididymis, sperm interact with secreted epididymal proteins that promote maturation, including the acquisition of motility and fertilization competence. Viewed previously as distinct from sperm maturation, host defence capabilities are now recognized functions of the human epididymis 2 (HE2) family of sperm-binding proteins. We analysed the potent dose and time-dependent bactericidal activity of recombinant HE2alpha, HE2beta1 and HE2beta2 and found that the full-length proteins (10 microg/ml or approximately 1 microM) caused more than a 50% decrease in Escherichia coli colony forming units within 15 min. By contrast, human beta-defensin-1, at a similar concentration, required more than 90 min to exhibit similar antibacterial activity. The epididymis-specific lipocalin, LCN6, failed to kill bacteria. Higher concentrations (25-100 microg/ml) of HE2 proteins and a longer duration of treatment resulted in near total inhibition of bacterial growth. The C-terminal peptides of HE2alpha, HEbeta1 and HEbeta2 proteins exhibited antibacterial activity similar to their full-length counterparts, indicating that the antibacterial activity of HE2 proteins resides in these C-terminal regions. Antibacterial activities of HE2 proteins and peptides were slightly inhibited by NaCl concentrations of up to 150 mM, while human beta-defensin-1 activity was nearly eliminated. Reduction and alkylation of disulphide bonds in HE2 proteins and their C-terminal peptides abolished their antibacterial activity. Consistent with the ability to kill bacteria, full-length HE2 proteins and C-terminal peptides caused rapid dose-dependent permeabilization of outer and cytoplasmic E. coli membranes. A much longer exposure time was required for human beta-defensin-1-mediated permeabilization of membranes, suggesting a possible difference in mode of action compared with the HE2 antibacterial peptides.
Yenugu
Suresh
S
Laboratories for Reproductive Biology, Department of Pediatrics, University of North Carolina, Chapel Hill 27599-7500, USA.
Hamil
Katherine G
KG
Birse
Charles E
CE
Ruben
Steven M
SM
French
Frank S
FS
Hall
Susan H
SH
D000478:Alkylation; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D000954:Antigens, Surface / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D015169:Colony Count, Microbial; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004822:Epididymis / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D006020:Glycopeptides / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D054835:Lipocalin 1; D008297:Male; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics* / Q000494:pharmacology*; D012661:Semen / Q000737:chemistry; D029589:Seminal Plasma Proteins; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride; D013094:Spermatozoa / Q000378:metabolism; D023083:beta-Defensins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D000954:Antigens, Surface; D002352:Carrier Proteins; D015853:Cysteine Proteinase Inhibitors; D006020:Glycopeptides; C518443:LCN1 protein, human; D054835:Lipocalin 1; D010446:Peptide Fragments; D020033:Protein Isoforms; D011994:Recombinant Proteins; C087044:SPAG11A protein, human; D029589:Seminal Plasma Proteins; D023083:beta-Defensins; C425042:spermadhesin; D012965:Sodium Chloride