These **data** suggested that RprY may play a role in regulating the heat shock response in P. gingivalis. We performed electrophoretic mobility shift assays (EMSA) to determine whether the regulation was due to direct binding of RprY to the promoter regions of the genes in question or an indirect effect because of RprY interaction with another regulator. DNA probes were generated by amplification of the 59 intergenic region upstream of the ORFs. DIG-labeled probes were incubated with increasing amount of phosphorylated rRprY protein (,0, 8.8, 17.6 and 35.2 pmol). Protein binding specificity was determined by adding 50-100X excess unlabeled probe to the reaction mixes. In these experiments the ahpC and sod promoters were used as positive and negative controls, respectively, as we previously showed that ahpC, but not sod, was a target of RprY [9]. By EMSA we showed that RprY bound to the promoter regions of groES, clpB and dnaK, but did not bind to the promoter region of htpG (Fig. 6B).