Crystal Structure of the Lysine Riboswitch Regulatory mRNA Element

Andrew D Garst,Annie Héroux,Robert P Rambo,Robert T Batey

doi:10.1074/jbc.c800120200

Abstract

Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch. Along with regulation of lysine biosynthetic genes, mutations within the lysine-responsive riboswitch (L-box) play a role in the acquisition of resistance to antimicrobial lysine analogs. To understand the structural basis for lysine binding, we have determined the 2.8 angstroms resolution crystal structure of lysine bound to the Thermotoga maritima asd lysine riboswitch ligand-binding domain. The structure reveals a complex architecture scaffolding a binding pocket completely enveloping lysine. Mutations conferring antimicrobial resistance cluster around this site as well as highly conserved long range interactions, indicating that they disrupt lysine binding or proper folding of the RNA. Comparison of the free and bound forms by x-ray crystallography, small angle x-ray scattering, and chemical probing reveals almost identical structures, indicating that lysine induces only limited and local conformational changes upon binding.

Highlights

Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch
To understand the structural basis for lysine binding, we have determined the 2.8 Aresolution crystal structure of lysine bound to the Thermotoga maritima asd lysine riboswitch ligand-binding domain
There at least 20 distinct families of riboswitches that recognize a diverse set of metabolites including nucleobases, sugars, vitamin cofactors, amino acids, and metal ions [2]

Summary

Introduction

Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch. Comparison of the free and bound forms by x-ray crystallography, small angle x-ray scattering, and chemical probing reveals almost identical structures, indicating that lysine induces only limited and local conformational changes upon binding.

Results

Conclusion