title: Catabolite regulation of the Bacillus subtilis ctaBCDEF gene cluster.
abstract: Bacillus subtilis cytochrome c oxidase caa3 is encoded by the ctaCDEF genes at the ctaABCDEF locus, with the ctaBCDEF genes organized as an operon-like unit. A dyad symmetry sequence and a catabolite response element homolog can be recognized in the 240-bp intercistronic region between ctaB and ctaC. ctaB'-lacZ and ctaBCD'-lacZ transcriptional fusions integrated at the native locus were used to study catabolite effects on transcription of the ctaB and ctaCDEF genes. In Schaeffer's medium lacking glucose, ctaBCD'-lacZ was expressed at a very low level during the exponential phase, and expression increased about 30-fold 2 h after entry into the stationary phase. In the presence of 0.5% glucose, ctaBCD'-lacZ expression was totally repressed. In contrast to ctaBCD'-lacZ, ctaB'-lacZ was constitutively expressed regardless of carbon source. The ctaCDEF genes were separated from ctaB by insertion of plasmids carrying selectable markers in such a way that the ctaCDEF and ctaB transcription units remained intact. Enzymatic assays of caa3 with these constructs, showed that ctaCDEF was not expressed independently of ctaB. Also, when a 'ctaB-ctaC'-lacZ fusion (containing the ctaB-ctaC intercistronic region) was placed at a remote nonessential locus, beta-galactosidase activity could not be detected. The absence of a promoter in the ctaB-ctaC intercistronic space also was indicated by the inability to detect ctaC-specific transcripts with RNase protection assays, primer extension, and rapid amplification of 5' cDNA ends. Direct mRNA measurements showed that, in the presence of 0.5% glucose, ctaBCDEF transcripts terminated at the 3' end of the putative stem-loop structure and the distal portion was down-regulated. A possible mechanism for ctaCDEF gene regulation is suggested. Catabolite repression of ctaBCD'-lacZ was partly dependent on CcpA but was independent of HPr. The expression of ctaBCDEF also appears to require the strC, ctaA, and resD-resE gene products.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Albany Medical College, Albany, New York 12201, USA.
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: H W
authors.initials: HW
authors.lastname: Taber
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D017931:DNA Primers / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005798:Genes, Bacterial; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D007763:Lac Operon; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D009690:Nucleic Acid Conformation; D009876:Operon; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics
chemical_list: D017931:DNA Primers; D012329:RNA, Bacterial; D003576:Electron Transport Complex IV; D005947:Glucose; D005990:Glycerol