Dual regulation of secretion system of periodontal virulence factors by novel two-component system and ECF sigma factor

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We investigated regulatory mechanism of secretion system of pathogenic proteases/ adhesins of the periodontopathogen Porphyromonas gingivalis. Secretion of P. gingivalis gingipain proteases/ adhesins depends on a protein secretion system, Por secretion system(PorSS). We isolated 12 gingipain secretion-deficient mutants and found that two of them were deficient in a two-component system, which is a prokaryotic signaling system and consists of the sensor histidine kinase PorY and response regulator PorX. In this study, we constructed recombinant PorY and PorX proteins and found that PorY was autophosphorylated and the phosphoryl residue of PorY was transferred to PorX. PorY could bind to PorX as revealed by Surface plasmon resonance(BIACORE) analysis. Gene expression of component proteins of the PorSS was also regulated by one of ECF sigma factors, PGN0274, but the PorY-PorX system and the PGN0274 sigma factor independently regulate gene expression of component proteins of the PorSS, suggesting that the PorSS is regulated by multiple regulatory mechanisms.