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Title: The activity of CouR, a MarR family transcriptional regulator, is modulated through a novel molecular mechanism

CouR, a MarR-type transcriptional repressor, regulates the cou genes, encoding p-hydroxycinnamate catabolism in the soil bacterium Rhodococcus jostii RHA1. The CouR dimer bound two molecules of the catabolite p-coumaroyl–CoA (Kd = 11 ± 1 μM). The presence of p-coumaroyl–CoA, but neither p-coumarate nor CoASH, abrogated CouR's binding to its operator DNA in vitro. The crystal structures of ligand-free CouR and its p-coumaroyl–CoA-bound form showed no significant conformational differences, in contrast to other MarR regulators. The CouR–p-coumaroyl–CoA structure revealed two ligand molecules bound to the CouR dimer with their phenolic moieties occupying equivalent hydrophobic pockets in each protomer and their CoA moieties adopting non-equivalent positions to mask the regulator's predicted DNA-binding surface. More specifically, the CoA phosphates formed salt bridges with predicted DNA-binding residues Arg36 and Arg38, changing the overall charge of the DNA-binding surface. The substitution of either arginine with alanine completely abrogated the ability of CouR to bind DNA. By contrast, the R36A/R38A double variant retained a relatively high affinity for p-coumaroyl–CoA (Kd = 89 ± 6 μM). Altogether, our data point to a novel mechanism of action in which the ligand abrogates the repressor's ability to bind DNA by steric occlusion of key DNA-binding residues and charge repulsionmore » of the DNA backbone.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [1] ;  [2] ;  [1]
  1. The Univ. of British Columbia, Vancouver, BC (Canada)
  2. Univ. of Toronto, Toronto, ON (Canada)
  3. Argonne National Lab. (ANL) and the Midwest Center for Structural Genomics, Lemont, IL (United States)
Publication Date:
OSTI Identifier:
1223714
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Nucleic Acids Research
Additional Journal Information:
Journal Name: Nucleic Acids Research; Journal ID: ISSN 0305-1048
Publisher:
Oxford University Press
Research Org:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES