7oig
CspA-27 cotranslational folding intermediate 3
Structural highlights
FunctionRL4_ECOLI One of the primary rRNA binding proteins, this protein initially binds near the 5'-end of the 23S rRNA. It is important during the early stages of 50S assembly. It makes multiple contacts with different domains of the 23S rRNA in the assembled 50S subunit and ribosome.[1] Protein L4 is a both a transcriptional repressor and a translational repressor protein; these two functions are independent of each other. It regulates transcription of the S10 operon (to which L4 belongs) by causing premature termination of transcription within the S10 leader; termination absolutely requires the NusA protein. L4 controls the translation of the S10 operon by binding to its mRNA. The regions of L4 that control regulation (residues 131-210) are different from those required for ribosome assembly (residues 89-103).[2] Forms part of the polypeptide exit tunnel.[3] Can regulate expression from Citrobacter freundii, Haemophilus influenzae, Morganella morganii, Salmonella typhimurium, Serratia marcescens, Vibrio cholerae and Yersinia enterocolitica (but not Pseudomonas aeruginosa) S10 leaders in vitro.[4] Publication Abstract from PubMedCellular proteins begin to fold as they emerge from the ribosome. The folding landscape of nascent chains is not only shaped by their amino acid sequence but also by the interactions with the ribosome. Here, we combine biophysical methods with cryo-EM structure determination to show that folding of a beta-barrel protein begins with formation of a dynamic alpha-helix inside the ribosome. As the growing peptide reaches the end of the tunnel, the N-terminal part of the nascent chain refolds to a beta-hairpin structure that remains dynamic until its release from the ribosome. Contacts with the ribosome and structure of the peptidyl transferase center depend on nascent chain conformation. These results indicate that proteins may start out as alpha-helices inside the tunnel and switch into their native folds only as they emerge from the ribosome. Moreover, the correlation of nascent chain conformations with reorientation of key residues of the ribosomal peptidyl-transferase center suggest that protein folding could modulate ribosome activity. A switch from alpha-helical to beta-strand conformation during co-translational protein folding.,Agirrezabala X, Samatova E, Macher M, Liutkute M, Maiti M, Gil-Carton D, Novacek J, Valle M, Rodnina MV EMBO J. 2022 Feb 15;41(4):e109175. doi: 10.15252/embj.2021109175. Epub 2022 Jan , 7. PMID:34994471[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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