Aerobic repression of the Rhodobacter capsulatus bchC promoter involves cooperative interactions between CrtJ bound to neighboring palindromes.
Previous studies demonstrated that bacteriochlorophyll, carotenoid, and light harvesting gene expression in Rhodobacter capsulatus is repressed under aerobic growth conditions by the repressor CrtJ. Isolated CrtJ is known to bind to the palindrome TGTN12ACA, which is present in two copies in the bchC promoter, one of which spans the -35 and the other the -10 sigma-70 recognition sequences. In this study, we demonstrate that CrtJ binds to the two palindromic sites in the bchC promoter in a cooperative manner. The level of cooperativity of CrtJ binding to the -35 palindrome was shown to be 26-fold. A distance of 8 base pairs between the two palindromic sites was shown to be critical for cooperative binding, as evidenced by the disruption of binding that resulted when +6 and +11 base pairs were inserted between the palindromes.
Ponnampalam
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Biochemistry Program, Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
Elsen
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Bauer
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D000332:Aerobiosis; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D016354:Rhodobacter capsulatus; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism*
D001426:Bacterial Proteins; C107183:CrtJ protein, Rhodobacter; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D010088:Oxidoreductases; C061969:2-desacetyl-2-hydroxyethyl bacteriochlorophyllide a dehydrogenase