DNA binding characteristics of RegA. A constitutively active anaerobic activator of photosynthesis gene expression in Rhodobacter capsulatus.
In the purple non-sulfur bacterium Rhodobacter capsulatus, RegA and RegB comprise a two-component regulatory system that is required for maximal anaerobic transcription of key photosynthesis genes. RegB is a sensor kinase that uses ATP to phosphorylate its cognate response regulator, RegA. The mechanism under which RegA approximately P influences transcription of target genes has been unclear given that past attempts to demonstrate DNA binding activity by isolated RegA have failed. This led to a model invoking a role for RegA approximately P as an intermediate in a more complex multicomponent phosphoryl transfer cascade. In the present study, we describe the isolation of a mutant version of RegA (RegA*) which promotes high level expression of photosynthesis genes independent of RegB. DNase I footprint analyses show that purified RegA* binds to the promoters of the puf and puc operons at locations that are consistent with RegA functioning as a transcriptional activator for these operons. We conclude that RegA functions, like most members of the response regulator family, as a DNA-binding protein that directly affects the expression of its target genes.
Du
S
S
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Bird
T H
TH
Bauer
C E
CE
D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon; D007785:Lactose / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011494:Protein Kinases; D016354:Rhodobacter capsulatus / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D045322:Photosynthetic Reaction Center Complex Proteins; C072722:RegA protein, Bacteria; C091081:RegB protein, Rhodobacter; D014157:Transcription Factors; D011494:Protein Kinases; D007785:Lactose