Nucleotide sequence analysis of the Streptococcus salivarius clpP locus revealed potential binding sites for both the CtsR and HrcA repressors. Dual regulation by HrcA and CtsR was demonstrated by using Bacillus subtilis as a heterologous host, and CtsR was shown to bind directly to the clpP promoter sequence. This is the first example of a clpP gene under the control of HrcA.