HrcA is commonly regarded as a class I transcriptional repressor, and its regulon was predicted in L. plantarum on the basis of a cognate cis-acting element, designated CIRCE, in the promoter regions of groEL-groES, hrcA-grpE-dnaK-dnaJ, and lp_0726 (61). Transcriptional regulation by HrcA is dependent on availability of the GroELS complex such that HrcA is inactive when GroELS is unavailable during periods of cellular stress (43).