The Bacillus subtilis catabolite control protein CcpA exerts all its regulatory functions by DNA-binding

In Bacillus subtilis, carbon catabolite control is mediated by the regulatory protein CcpA. In addition to loss of catabolite repression, ccpA mutants exhibit a severe growth defect. They are not able to grow with glucose and ammonium as single sources of carbon and nitrogen, respectively. Only ccpA mutant strains carrying either secondary suppressor mutations or that are affected in specific amino acids in the DNA-binding domain of CcpA grow on minimal media. We addressed the importance of DNA-binding by CcpA for both carbon catabolite repression and growth of a mutant strain. A strain specifically deleted for the N-terminal DNA-binding domain of CcpA was constructed. This deletion resulted in complete loss of catabolite repression of beta-xylosidase synthesis and prevented bacteria from growing on minimal media, suggesting that DNA-binding by CcpA is required for both carbon catabolite repression and efficient growth on minimal media.