Dynamic multidrug recognition by multidrug transcriptional repressor LmrR.

Area of Science:

• Molecular Biology
• Structural Biology
• Microbial Physiology

Background:

• LmrR is a transcriptional repressor regulating the LmrCD multidrug transporter in Lactococcus lactis.
• The mechanism of LmrR's recognition of diverse compounds and its release from DNA is not fully understood.
• Understanding LmrR's function is key to deciphering multidrug resistance mechanisms in bacteria.

Purpose of the Study:

• To structurally and dynamically characterize LmrR in its apo, compound-bound, and promoter-bound states.
• To elucidate the molecular mechanisms underlying LmrR's promiscuous multidrug recognition.
• To understand how compound binding influences LmrR's interaction with its DNA promoter.

Main Methods:

• Structural characterization of LmrR using biophysical techniques.
• Dynamic analysis of LmrR in different functional states (apo, ligand-bound, DNA-bound).
• Investigation of conformational ensembles and their role in ligand and DNA binding.

Main Results:

• The compound-binding site of LmrR displays significant dynamics in the apo state.
• Compound binding shifts conformational equilibria, enabling recognition of structurally unrelated molecules.
• Allosteric site dynamics are redistributed upon compound binding, favoring high-affinity recognition through entropy.
• Incompatible conformational ensembles between compound- and promoter-bound states mediate reciprocal binding.

Conclusions:

• LmrR utilizes dynamic conformational ensembles for promiscuous multidrug recognition and transcriptional repression.
• A static structural view is insufficient to explain LmrR's functional mechanism.
• The study provides insights into how dynamic interactions govern the function of multidrug resistance regulators.