|Genome-wide identification of in vivo binding sites of GlxR, a cyclic AMP receptor protein-type regulator in
J. Bacteriol. 193: 4123-4133. 2011.
K. Toyoda, H. Teramoto, M. Inui and H. Yukawa.
|Corynebacterium glutamicum GlxR is a cyclic AMP (cAMP) receptor protein-type regulator. Although
over 200 GlxR-binding sites in the C. glutamicum genome are predicted in silico, studies on the physiological function of GlxR have been hindered by the
severe growth defects of a glxR mutant. This study identified the GlxR regulon by chromatin immunoprecipitation in conjunction with microarray (ChIP-chip) analyses. In total, 209 regions were detected as in vivo GlxR-binding sites. In vitro binding assays and promoter-reporter assays demonstrated that GlxR directly
activates expression of genes for aerobic respiration, ATP synthesis, and
glycolysis and that it is required for expression of genes for cell separation
and mechanosensitive channels. GlxR also directly represses a citrate uptake
gene in the presence of citrate. Moreover, ChIP-chip analyses showed that
GlxR was still able to interact with its target sites in a mutant with
a deletion of cyaB, the sole adenylate cyclase gene in the genome, even though binding affinity
was markedly decreased. Thus, GlxR is physiologically functional at the
relatively low cAMP levels in the cyaB mutant, allowing the cyaB mutant to grow much better than the glxR mutant.