Funding Organization(s): European Research Council (ERC), National Science Foundation (NSF, United States), National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
Primary Citation of Related Structures: 7O19, 7O1A, 7O1C
PubMed Abstract:
Free L-tryptophan (L-Trp) stalls ribosomes engaged in the synthesis of TnaC, a leader peptide controlling the expression of the Escherichia coli tryptophanase operon. Despite extensive characterization, the molecular mechanism underlying the recognition and response to L-Trp by the TnaC-ribosome complex remains unknown. Here, we use a combined biochemical and structural approach to characterize a TnaC variant (R23F) with greatly enhanced sensitivity for L-Trp. We show that the TnaC-ribosome complex captures a single L-Trp molecule to undergo termination arrest and that nascent TnaC prevents the catalytic GGQ loop of release factor 2 from adopting an active conformation at the peptidyl transferase center. Importantly, the L-Trp binding site is not altered by the R23F mutation, suggesting that the relative rates of L-Trp binding and peptidyl-tRNA cleavage determine the tryptophan sensitivity of each variant. Thus, our study reveals a strategy whereby a nascent peptide assists the ribosome in detecting a small metabolite.
Organizational Affiliation:
Univ. Bordeaux, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, ARNA, UMR 5320, U1212, Institut Européen de Chimie et Biologie, Pessac, France.
Department of Biological Sciences, University of Alabama in Huntsville, Huntsville, AL, USA.
Department of Biology, Texas A&M University, College Station, TX, USA.
Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL, USA.
Department of Biology, Texas A&M University, College Station, TX, USA. msachs@bio.tamu.edu.
Department of Biological Sciences, University of Alabama in Huntsville, Huntsville, AL, USA. lrc0002@uah.edu.
Univ. Bordeaux, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, ARNA, UMR 5320, U1212, Institut Européen de Chimie et Biologie, Pessac, France. axel.innis@inserm.fr.
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