Solution structure of the carbon storage regulator protein CsrA from Escherichia coli

Abstract

The carbon storage regulator A (CsrA) is a protein responsible for the repression of a variety of stationary-phase genes in bacteria. In this work, we describe the nuclear magnetic resonance (NMR)-based structure of the CsrA dimer and its RNA-binding properties. CsrA is a dimer of two identical subunits, each composed of five strands, a small α-helix and a flexible C terminus. NMR titration experiments suggest that the β1-β2 and β3-β4 loops and the C-terminal helix are important elements in RNA binding. Even though the β3-β4 loop contains a highly conserved RNA-binding motif, GxxG, typical of KH domains, our structure excludes CsrA from being a member of this protein family, as previously suggested. A mechanism for the recognition of mRNAs downregulated by CsrA is proposed. Copyright © 2005, American Society for Microbiology. All Rights Reserved.