FIG 5.

ArcA directly regulates the expression of motA, motB, and cheA. (A) The motA, motB, and cheA genes form one operon, as represented by RT-PCR results using cDNA and a negative control without reverse transcriptase. Primers were designed to span open reading frames (ORFs) motA and motB, motB and cheA, and cheA and cheW. RNA was purified and reverse transcribed to cDNA. The RNA that was not reverse transcribed served as a negative control. (B) Nonradioactive EMSA of binding of ArcA-His6 to the promoter regions of motA, motB, and cheA. PCR products of the motA promoter region were used as probes at 50 ng per reaction mixture. Purified ArcA-His6 fusion protein was added to each reaction mixture at different concentrations, as indicated; the coding-region DNA probes with and without the ArcA protein were used as negative controls. DNA fragments were stained with SYBR green.