Transcriptional cross-regulation between gram-negative and gram-positive bacteria, demonstrated using argP-argO of Escherichia coli and LysG-lysE of Corynebacterium glutamicum

Abstract

The protein-gene pairs ArgP-argO of Escherichia coli and LysG-lysE of Corynebacterium glutamicum are orthologous, with the first member of each pair being a LysR-type transcriptional regulator and the second its target gene encoding a basic amino acid exporter. Whereas LysE is an exporter of arginine (Arg) and lysine (Lys) whose expression is induced by Arg, Lys, or histidine (His), ArgO exports Arg alone, and its expression is activated by Arg but not Lys or His. We have now reconstituted in E. coli the activation of lysE by LysG in the presence of its coeffectors and have shown that neither ArgP nor LysG can regulate expression of the noncognate orthologous target. Of several ArgP-dominant (ArgPd) variants that confer elevated Arg-independent argO expression,some (ArgPd-P274S, -S94L,and, to a lesser extent, -P108S) activated lysE expression in E. coli. However, the individual activating effects of LysG and ArgPd on lysE were mutually extinguished when both proteins were coexpressed in Arg- or Hissupplemented cultures. In comparison with native ArgP, the active ArgPd variants exhibited higher affinity of bindingto the lysE regulatory region and less DNA bending at both argO and lysE. We conclude that the transcription factor LysG from a Grampositive bacterium, C. glutamicum, is able toengage appropriatelywith the RNA polymerase from a Gram-negative bacterium, E. coli, for activation of its cognate target lysE in vivo and that single-amino-acid-substitution variants of ArgP can also activate the distantly orthologous target lysE, but by a subtly different mechanism that renders them noninterchangeable with LysG. © 2012, American Society for Microbiology.