6bz8
From Proteopedia
Thermus thermophilus 70S containing 16S G347U point mutation and near-cognate ASL Leucine in A site
Structural highlights
FunctionRS13_THET8 Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome structure it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the top of the two subunits; these bridges are in contact with the A site and P site tRNAs respectively and are implicated in movement during ribosome translocation. Separately contacts the tRNAs in the A and P sites.[HAMAP-Rule:MF_01315] Publication Abstract from PubMedDecoding is thought to be governed by a conformational transition in the ribosome-open (off) to closed (on)-that occurs upon codon-anticodon pairing in the A site. Ribosomal ambiguity (ram) mutations increase miscoding and map to disparate regions, consistent with a role for ribosome dynamics in decoding, yet precisely how these mutations act has been unclear. Here, we solved crystal structures of 70S ribosomes harboring 16S ram mutations G299A and G347U in the absence A-site tRNA (A-tRNA) and in the presence of a near-cognate anticodon stem-loop (ASL). In the absence of an A-tRNA, each of the mutant ribosomes exhibits a partially closed (on) state. In the 70S-G347U structure, the 30S shoulder is rotated inward and intersubunit bridge B8 is disrupted. In the 70S-G299A structure, the 30S shoulder is rotated inward and decoding nucleotide G530 flips into the anti conformation. Both of these mutant ribosomes adopt the fully closed (on) conformation in the presence of near-cognate A-tRNA, just as they do with cognate A-tRNA. Thus, these ram mutations act by promoting the open (off) to closed (on) transition, albeit in somewhat distinct ways. This work reveals the functional importance of 30S shoulder rotation for productive aminoacylated-tRNA incorporation. Ribosomal ambiguity (ram) mutations promote the open (off) to closed (on) transition and thereby increase miscoding.,Hoffer ED, Maehigashi T, Fredrick K, Dunham CM Nucleic Acids Res. 2018 Nov 22. pii: 5198528. doi: 10.1093/nar/gky1178. PMID:30476222[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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