title: Antimicrobial activity and molecular mechanism of the CRES protein.
abstract: Cystatin-related epididymal spermatogenic (CRES) protein, a member of the cystatin superfamily of cysteine protease inhibitors (also known as CST8), exhibits highly specific, age-dependent expression in mouse testis and epididymis. The CRES protein possesses four highly conserved cysteine residues which govern the overall conformation of the cystatins through the formation of two disulfide bonds. Previous studies have revealed that other cystatin family members, such as cystatin 3 and cystatin 11, show antibacterial activity in vitro. This prompted us to investigate the potential antimicrobial activity of the CRES protein. Colony forming assays and spectrophotometry were used to investigate the effects of recombinant CRES protein on Escherichia coli (E. coli) and Ureaplasma urealyticum (Uu), respectively, in vitro. After incubation of E. coli with CRES recombinant protein fused with glutathione-S-transferase (GST), a substantial decrease in colony forming units was observed, and the effect was dose and time dependent. Furthermore, it took longer for Uu to grow to plateau stage when incubated with GST-CRES recombinant protein compared with the control GST. The antibacterial and Anti-Uu activities were not impaired when the cysteine residues of CRES protein were mutated, indicating that the antimicrobial effect was not dependent on its disulfide bonds. Functional analysis of three CRES polypeptides showed that the N-terminal 30 residues (N30) had no antimicrobial activity while N60 showed similar activity as full-length CRES protein. These results suggest that the active center of CRES protein resides between amino acid residues 31 and 60 of its N-terminus. Mechanistically, E. coli membrane permeabilization was increased in a dose-dependent manner, and macromolecular synthesis was inhibited on treatment with GST-CRES. Together, our data on the antimicrobial activities of CRES protein suggest that it is a novel and innate antimicrobial protein which protecting the male reproductive tract against invading pathogens.
authors.affiliation: Department of Histology and Embryology, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Qing
authors.initials: Q
authors.lastname: Yuan
authors.forename: Sunhong
authors.initials: S
authors.lastname: Chen
authors.forename: Heng
authors.initials: H
authors.lastname: Cai
authors.forename: Meige
authors.initials: M
authors.lastname: Lu
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.forename: Chen
authors.initials: C
authors.lastname: Xu
mesh_terms: D015057:1-Naphthylamine / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001681:Biological Assay; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003001:Cloning, Molecular; D015891:Cystatins / Q000378:metabolism* / Q000494:pharmacology*; D003545:Cysteine / Q000235:genetics; D004822:Epididymis / Q000166:cytology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure; D046911:Macromolecular Substances / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000378:metabolism; D014509:Ureaplasma / Q000187:drug effects
chemical_list: D000890:Anti-Infective Agents; D015891:Cystatins; D046911:Macromolecular Substances; D010446:Peptide Fragments; C078310:Cst8 protein, mouse; C005444:N-phenyl-1-naphthylamine; D015057:1-Naphthylamine; D003545:Cysteine