3a). Because gingipain activity can be regulated at the transcriptional and post-transcriptional levels (Tokuda et al., 1998), oligonucleotide primers, as described previously

(Vanterpool et al., 2005a), were used in RT-PCR analysis to determine whether these two sigma factors were involved in the transcriptional regulation of gingipain-encoding Y27632 genes. As shown in Fig. 3b, the inactivation of PG0162 and PG1660 had no effect on the expression of rgpA, rgpB, or kgp at the transcriptional level. In FLL355 (PG1827∷ermF), the Kgp activity showed a 25% increase over the wild type. No change was observed in the transcription of the kgp gene in FLL355 (data not shown). Taken together, these results suggest that ECF sigma factors may be involved in the post-transcriptional regulation of gingipains. Post-transcriptional regulation of the gingipains in P. gingivalis is associated with its maturation pathway, which is linked to the biosynthesis Panobinostat mw of surface carbohydrates (Shoji et al., 2002; Paramonov et al., 2005) and several other proteins including the PorR (Shoji et al., 2002), PorT (Sato et al., 2005; Nguyen et al., 2009),

Sov (Saiki & Konishi, 2010), and VimA (Vanterpool et al., 2006). It is unclear how these factors are modulated by the ECF sigma factors and is an active area of further exploration in the laboratory. The correlation between gingipain activity and hemagglutination in P. gingivalis (Lewis et al., 1999; Shi et al., 1999; Vanterpool et al., 2005a) is related to the similar adhesion domains encoded by the hagA, rgpA, and kgp genes (Chen & Duncan, 2004). The hemagglutination potential of ECF sigma factor-defective mutants was assessed. In comparison with the wild-type strain, there was a decrease Aprepitant in the hemagglutination activity in all the mutants. In FLL350, the level of hemagglutination activity was comparable

to the negative control. This is in contrast to FLL354, which showed the greatest reduction in gingipain activity, but a higher hemagglutination activity. RT-PCR using hagA-specific primers indicated no change in the expression of that gene in FLL350 (Fig. 4c). While gingipains have been observed to have hemolytic activity (Shah & Gharbia, 1989; Lewis et al., 1999), hemolysin can be independent of their catalytic association (Deshpande & Khan, 1999). Several putative hemolysin genes have been identified in the P. gingivalis genome (Nelson et al., 2003) and cloned in E. coli (Karunakaran & Holt, 1993). The hemolysins produced by P. gingivalis provide the bacterium with heme-containing molecules that are required for their in vivo survival. Hemolytic activities of all the ECF-defective mutants in this study were similar to those of the wild type, except for FLL350 (Fig. 4d). The FLL350 mutant showed a 50% reduction in those activities compared with the parent strain.