4uy8
From Proteopedia
Molecular basis for the ribosome functioning as a L-tryptophan sensor - Cryo-EM structure of a TnaC stalled E.coli ribosome
Structural highlights
FunctionRL2_ECOLI One of the primary rRNA binding proteins. Located near the base of the L1 stalk, it is probably also mobile. Required for association of the 30S and 50S subunits to form the 70S ribosome, for tRNA binding and peptide bond formation. It has been suggested to have peptidyltransferase activity; this is highly controversial.[HAMAP-Rule:MF_01320_B] In the E.coli 70S ribosome in the initiation state it has been modeled to make several contacts with the 16S rRNA (forming bridge B7b, PubMed:12809609); these contacts are broken in the model with bound EF-G.[HAMAP-Rule:MF_01320_B] Publication Abstract from PubMedElevated levels of the free amino acid L-tryptophan (L-Trp) trigger expression of the tryptophanase tnaCAB operon in E. coli. Activation depends on tryptophan-dependent ribosomal stalling during translation of the upstream TnaC peptide. Here, we present a cryoelectron microscopy (cryo-EM) reconstruction at 3.8 A resolution of a ribosome stalled by the TnaC peptide. Unexpectedly, we observe two L-Trp molecules in the ribosomal exit tunnel coordinated within composite hydrophobic pockets formed by the nascent TnaC peptide and the tunnel wall. As a result, the peptidyl transferase center (PTC) adopts a distinct conformation that precludes productive accommodation of release factor 2 (RF2), thereby inducing translational stalling. Collectively, our results demonstrate how the translating ribosome can act as a small molecule sensor for gene regulation. Molecular Basis for the Ribosome Functioning as an L-Tryptophan Sensor.,Bischoff L, Berninghausen O, Beckmann R Cell Rep. 2014 Oct 7. pii: S2211-1247(14)00779-7. doi:, 10.1016/j.celrep.2014.09.011. PMID:25310980[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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