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From Proteopedia
2.9 A cryo-EM structure of VemP-stalled ribosome-nascent chain complex
Structural highlights
FunctionRS11_ECOLI Located on the platform of the 30S subunit, it bridges several disparate RNA helices of the 16S rRNA. Forms part of the Shine-Dalgarno cleft in the 70S ribosome (By similarity).[HAMAP-Rule:MF_01310] Publication Abstract from PubMedInteraction between the nascent polypeptide chain and the ribosomal exit tunnel can modulate the rate of translation and induce translational arrest to regulate expression of downstream genes. The ribosomal tunnel also provides a protected environment for initial protein folding events. Here, we present a 2.9 A cryo-electron microscopy structure of a ribosome stalled during translation of the extremely compacted VemP nascent chain. The nascent chain forms two alpha-helices connected by an alpha-turn and a loop, enabling a total of 37 amino acids to be observed within the first 50-55 A of the exit tunnel. The structure reveals how alpha-helix formation directly within the peptidyltransferase center of the ribosome interferes with aminoacyl-tRNA accommodation, suggesting that during canonical translation, a major role of the exit tunnel is to prevent excessive secondary structure formation that can interfere with the peptidyltransferase activity of the ribosome. The force-sensing peptide VemP employs extreme compaction and secondary structure formation to induce ribosomal stalling.,Su T, Cheng J, Sohmen D, Hedman R, Berninghausen O, von Heijne G, Wilson DN, Beckmann R Elife. 2017 May 30;6. pii: e25642. doi: 10.7554/eLife.25642. PMID:28556777[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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