This Article Full Text (PDF) Other Versions of this Article: JB.01456-07v1 190/4/1237    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by MacLean, A. M. Articles by Finan, T. M. Search for Related Content PubMed PubMed Citation Articles by MacLean, A. M. Articles by Finan, T. M.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.01456-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Binding site determinants for the LysR-type transcriptional regulator PcaQ in the legume endosymbiont Sinorhizobium meliloti

Center for Environmental Genomics, Department of Biology, McMaster University. Hamilton, Ontario, Canada

^* To whom correspondence should be addressed. Email: finan{at}mcmaster.ca.

	Abstract

LysR-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. In the Gram-negative legume endosymbiont Sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the -ketoadipate pathway are encoded within the pcaDCHGB operon, which is subject to regulation by the LysR-type protein PcaQ. In this work, purified PcaQ is shown to bind strongly (K_D:0.54 nM) to a region -78 to -45 upstream of the pcaD transcriptional start site. Within this region, we have defined a PcaQ-binding site of dyad symmetry that is required for regulation of pcaD expression in vivo and for binding of PcaQ in vitro. We also demonstrate that PcaQ participates in negative auto-regulation by monitoring expression of pcaQ via a transcriptional fusion to lacZ. Although pcaQ homologues are present in many -proteobacteria, this work details the first reported purification of this regulator, as well as a characterization of its binding site, which is conserved in Agrobacterium tumefaciens, Rhizobium leguminosarum, R. etli, and Mesorhizobium loti.