Interaction of CbbR and RegA* transcription regulators with the Rhodobacter sphaeroides cbbIPromoter-operator region.
The form I (cbb(I)) Calvin-Benson-Bassham (CBB) reductive pentose phosphate cycle operon of Rhodobacter sphaeroides is regulated by both the transcriptional activator CbbR and the RegA/PrrA (RegB/PrrB) two-component signal transduction system. DNase I footprint analyses indicated that R. sphaeroides CbbR binds to the cbb(I) promoter between -10 and -70 base pairs (bp) relative to the cbb(I) transcription start. A cosmid carrying the R. capsulatus reg locus was capable of complementing an R. sphaeroides regA-deficient mutant to phototrophic growth with restored regulated synthesis of both photopigments and ribulose-bisphosphate carboxylase/oxygenase (Rubisco). DNase I footprint analyses, using R. capsulatus RegA*, a constitutively active mutant version of RegA, detected four RegA* binding sites within the cbb(I) promoter. Two sites were found within a previously identified cbb(I) promoter proximal regulatory region from -61 to -110 bp. One of these proximal RegA* binding sites overlapped that of CbbR. Two sites were within a previously identified promoter distal positive regulatory region between -301 and -415 bp. Expression from promoter insertion mutants showed that the function of the promoter distal regulatory region was helical phase-dependent. These results indicated that RegA exerts its regulatory affect on cbb(I) expression through direct interaction with the cbb(I) promoter.
Dubbs
J M
JM
Department of Microbiology and Plant Biotechnology Center, The Ohio State University, Columbus, Ohio 43210-1292, USA.
Bird
T H
TH
Bauer
C E
CE
Tabita
F R
FR
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C072722:RegA protein, Bacteria; D014157:Transcription Factors; C072714:cfxR protein, bacteria