The
Bacillus subtilis yrkP gene encodes a response regulator of a two-component regulatory system of unknown function. A previous DNA microarray experiment suggested that multicopy
yrkP greatly enhanced the expression of
yrkN, the
ykcBC operon, and
yrkO, which encodes a putative transporter. Here,
lacZ fusion analysis confirmed these results and also revealed that YrkP autoregulates the putative
yrkPQR operon, indicating that
yrkPQR and
yrkO form a divergon structure. In addition, real-time PCR analysis revealed that transcription of
yrkO,
yrkN, and
ykcBC was significantly reduced in the
yrkP strain. Hence, YrkP positively regulates the expression of these genes. Gel retardation analyses showed that YrkP bound to the promoter regions of
yrkO,
yrkN, and
ykcB, albeit with lower binding affinities to the latter two promoters. The
in vitro binding of YrkP to the promoter region of the
yrkPQR and
yrkO divergon was then analyzed by DNase I footprinting analysis. This revealed that YrkP recognizes three regions containing single-motifs or a direct repeat of the ten-base sequence [T/G]TCA[T/C]AAATT.
lacZ fusion analysis of deleted and mutagenized promoter regions of
yrkO and
yrkPQR divergon confirmed that the three YrkP-binding regions are needed for the YrkP-mediated activation of
yrkO and/or
yrkPQR.
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