Identification of the srtC1 transcription start site and catalytically essential residues required for Actinomyces oris T14V SrtC1 activity.

In Actinomyces oris T14V, sortase SrtC1 mediates the assembly of type 1 fimbriae. We analyzed the effects of the conserved residues (H184, H204, F213, Y236, L263, T265, C266 and R275) on the SrtC1 activity by site-directed mutagenesis. We identified three essential conserved residues (H204, Y236 and C266) that are critical for the assembly of type 1 fimbriae in this organism. rapid amplification of cDNA ends analyses and reverse transcriptase-PCR results indicate that srtC1 was transcribed together with the putative adhesin gene fimQ and major structural subunit gene fimP as a single polycistronic mRNA.