Dynamic multidrug recognition by multidrug transcriptional repressor LmrR.

Koh Takeuchi,Koh Takeuchi,Ichio Shimada,Ichio Shimada,Yuji Tokunaga,Yuji Tokunaga,Yuji Tokunaga,Misaki Imai,Hideo Takahashi,Hideo Takahashi

doi:10.1038/srep06922

Abstract

LmrR is a multidrug transcriptional repressor that controls the expression of a major multidrug transporter, LmrCD, in Lactococcus lactis. However, the molecular mechanism by which LmrR binds to structurally unrelated compounds and is released from the promoter region remains largely unknown. Here, we structurally and dynamically characterized LmrR in the apo, compound-bound and promoter-bound states. The compound-binding site of LmrR exhibits ps–μs dynamics in the apo state, and compound ligation shifts the preexisting conformational equilibrium to varying extents to achieve multidrug recognition. Meanwhile, the compound binding induces redistribution of ps–ns dynamics to the allosteric sites, which entropically favors the high-affinity recognition. Furthermore, the reciprocal compound/promoter binding by LmrR is achieved by the incompatible conformational ensembles between the compound- and promoter-bound states. Collectively, the data show how LmrR can dynamically exert its functions through promiscuous multi-target interactions, in a manner that cannot be understood by a static structural view.

Highlights

LmrR is a multidrug transcriptional repressor that controls the expression of a major multidrug transporter, LmrCD, in Lactococcus lactis
A Gram-positive bacterium, Lactococcus lactis, exhibits multidrug resistance (MDR) when exposed to increasing concentrations of structurally unrelated toxic compounds, such as Hoechst 33342 (H33342), daunomycin, ethidium, and rhodamine 6G (Rho6G)[7,8] (Fig. 1a)
To characterize the dynamic nature of LmrR, we subjected the protein to solution NMR measurements

Summary

Introduction

LmrR is a multidrug transcriptional repressor that controls the expression of a major multidrug transporter, LmrCD, in Lactococcus lactis. The expression of multidrug transporters is strictly regulated by transcriptional activators and/or repressors, which tend to have the ability to bind multiple toxic compounds[4]. When the cells are exposed to the toxic compounds, LmrR is released from the promoter regions to induce membrane expression of the transporter[12]. The structural analysis of LmrR in the promoterbound state as well as in the compound-bound states in solution, without any distortion caused by experimental conditions, is required, to reveal the molecular mechanism by which LmrR binds to various structurally unrelated compounds and is released from the promoter region to show the MDR phenotype

Methods

Results

Conclusion