Catabolite repression mediated by the catabolite control protein CcpA in Staphylococcus xylosus.

Abstract

The gene ccpA encoding the catabolite control protein CcpA of Staphylococcus xylosus has been cloned and characterized. The CcpA protein belongs to the Lacl/GaiR family of bacterial regulators and is comprised of 329 amino acids, with a molecular mass of 36.3 kDa. It shows 56% identity with the CcpA proteins of Bacillus subtills and Bacillus megaterium. Inactivation of the ccpA gene in the genome of S. xylosus relieved the activities of three enzymes, alpha-glucosidase, beta-glucuronidase, and beta-galactosidase, from cataboilte repression by several carbohydrates. Concomitantly, transcription initiation of the maltose-utilization operon malRA, including the alpha-glucosidase gene malA, was no longer subject to glucose-specific control. Carbon source-dependent malRA regulation was also lost upon deletion of a palindromic sequence in the malRA promoter region resembling the catabolite-responsive elements essential for CcpA-dependent catabolite repression in Bacillus. These results strongly suggest that S. xylosus CcpA controls transcription of catabolite-repressible genes and operons by binding to catabolite-responsive operators when rapidly metabolizable carbohydrates are available. Accordingly, the cloned S. xylosus ccpA gene could complement the ccpA mutation in B. subtilis. The ccpA gene of S. xylosus is transcribed from two promoters, one of which is subject to autogenous repression by CcpA. Autoregulation results in a slight reduction of CcpA protein in glucose-grown cells. The characterization of the role of CcpA in carbon catabolite repression in S. xylosus demonstrates that a regulatory mechanism originally detected in Bacillus applies to another Gram-positive bacterium with low GC content.