Sy. Du et al., DNA-BINDING CHARACTERISTICS OF REGA - A CONSTITUTIVELY ACTIVE ANAEROBIC ACTIVATOR OF PHOTOSYNTHESIS GENE-EXPRESSION IN RHODOBACTER-CAPSULATUS, The Journal of biological chemistry, 273(29), 1998, pp. 18509-18513
In the purple non-sulfur bacterium Rhodobacter capsulatus, RegA and Re
gB comprise a two-component regulatory system that is required for max
imal anaerobic transcription of key photosynthesis genes. RegB is a se
nsor kinase that uses ATP to phosphorylate its cognate response regula
tor, RegA, The mechanism under which RegA similar to P influences tran
scription of target genes has been unclear given that past attempts to
demonstrate DNA binding activity by isolated RegA have failed. This l
ed to a model invoking a role for RegA similar to 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 in
dependent of RegB. DNase I footprint analyses show that purified RegA
binds to the promoters of the puf and puc operons at locations that a
re 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.