| Abstrakt: |
ABSTRACTStudies in our laboratory have identified two fimbria-associated adhesins, FimA and Fap1, of Streptococcus parasanguisFW213. In this study, we isolated and sequenced DNA fragments linked tofimAto determine if they contained additional factors associated with adherence, virulence, or survival in the host. An open reading frame just upstream and divergently transcribed from thefimAoperon was identified and named pepO. Northern hybridization indicated that pepOis transcribed as a monocistronic message. pepOencodes a predicted 631-amino-acid protein with a molecular mass of approximately 70.6 kDa. PepO contains the essential motif HEXXH, typical of many zinc-dependent metalloproteases and metallopeptidases. PepO has significant sequence identity to mammalian metallopeptidases, including endothelin-converting enzyme, which converts a potent vasoconstrictor into its active form, and neutral endopeptidase (NEP), which is involved in terminating the activity of opioid peptides. The opioid peptide metenkephalin is a natural substrate of NEP. Cell extracts of FW213 cleaved metenkephalin at the same site as does NEP, while an extract from an insertionally inactivated pepOmutant did not. These results indicate that FW213 pepOencodes an enzyme with activity similar to that of known mammalian endopeptidases. Phylogenetic analysis of PepO and its homologues suggests lateral genetic exchange between bacteria and eukaryotes. |
