title: Mutation-Induced Population Shift in the MexR Conformational Ensemble Disengages DNA Binding: A Novel Mechanism for MarR Family Derepression.
abstract: MexR is a repressor of the MexAB-OprM multidrug efflux pump operon of Pseudomonas aeruginosa, where DNA-binding impairing mutations lead to multidrug resistance (MDR). Surprisingly, the crystal structure of an MDR-conferring MexR mutant R21W (2.19 Å) presented here is closely similar to wild-type MexR. However, our extended analysis, by molecular dynamics and small-angle X-ray scattering, reveals that the mutation stabilizes a ground state that is deficient of DNA binding and is shared by both mutant and wild-type MexR, whereas the DNA-binding state is only transiently reached by the more flexible wild-type MexR. This population shift in the conformational ensemble is effected by mutation-induced allosteric coupling of contact networks that are independent in the wild-type protein. We propose that the MexR-R21W mutant mimics derepression by small-molecule binding to MarR proteins, and that the described allosteric model based on population shifts may also apply to other MarR family members.
authors.affiliation: Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden.
authors.forename: Madhanagopal
authors.initials: M
authors.lastname: Anandapadamanaban
authors.affiliation: Division of Bioinformatics, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Pilstål
authors.affiliation: Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Andresen
authors.affiliation: Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden; School of Molecular Bioscience, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Jill
authors.initials: J
authors.lastname: Trewhella
authors.affiliation: Department of Medical Biochemistry and Biophysics, Protein Science Facility, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Moche
authors.affiliation: Division of Bioinformatics, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Wallner
authors.affiliation: Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping, Sweden. Electronic address: maria.sunnerhagen@liu.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Sunnerhagen
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D056004:Molecular Dynamics Simulation; D009154:Mutation; D009876:Operon; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D054730:Protein Interaction Domains and Motifs; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053838:Scattering, Small Angle; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C423620:MexR protein, Pseudomonas aeruginosa; D011994:Recombinant Proteins; D012097:Repressor Proteins