ANALYSIS OF CCPA MUTATIONS DEFECTIVE IN CARBON CATABOLITE REPRESSION IN BACILLUS-MEGATERIUM

Five mutations in ccpA of Bacillus megaterium with impaired functions were analysed for carbon catabolite repression. The phenotypes support the hypothesis that CcpA assumes a PurR/LacI fold. The completely ina ctive mutants CcpA119GE and CcpA326am cause alterations which are inco mpatible with that fold. A mutation with reduced activity, CcpA81GE, a ffects a site that would be partially surface exposed and may interfer e with structure formation or cofactor binding. A mutation in the puta tive hinge alpha-helix, CcpA52AE, is negative transdominant over wild- type ccpA. The mutant CcpA38am is inactive, although reduced amounts o f wild-type size protein are produced.