Antagonistic Roles for GcvA and GcvB inhdeABExpression inEscherichia coli

Abstract

InE. coli, the periplasmic proteins HdeA and HdeB have chaperone-like functions, suppressing aggregation of periplasmic proteins under acidic conditions. A microarray analysis of RNA isolated from anE. coliwild type and a ΔgcvB strain grown to mid-log phase in Luria-Bertani broth indicated thehdeABoperon, encoding the HdeA and HdeB proteins, is regulated by the sRNA GcvB. We wanted to verify that GcvB and its coregulator Hfq play a role in regulation of thehdeABoperon. In this study, we show that GcvB positively regulateshdeA::lacZandhdeB::lacZtranslational fusions in cells grown in Luria-Bertani broth and in glucose minimal media + glycine. Activation also requires the Hfq protein. Although many sRNAs dependent on Hfq regulate by an antisense mechanism, GcvB regulateshdeABeither directly or indirectly at the level of transcription. GcvA, the activator ofgcvB, negatively regulateshdeABat the level of transcription. Although expression ofgcvBis dependent on GcvA, activation ofhdeABby GcvB occurs independently of GcvA’s ability to repress the operon. Cell survival and growth at low pH are consistent with GcvA negatively regulating and GcvB positively regulating thehdeABoperon.