7oii
From Proteopedia
CspA-70 cotranslational folding intermediate 2
Structural highlights
FunctionRL22_ECOLI This protein binds specifically to 23S rRNA; its binding is stimulated by other ribosomal proteins, e.g. L4, L17, and L20. 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.[HAMAP-Rule:MF_01331_B] The globular domain of the protein is one of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit, while an extended beta-hairpin is found that penetrates into the center of the 70S ribosome where it lines the wall of the exit tunnel. Removal of most of this hairpin (residues 85-95) does not prevent its incorporation into 70S ribosomes. Two of the hairpin residues (91 and 93) seem to be involved in translation elongation arrest of the SecM protein, as their replacement by larger amino acids alleviates the arrest.[HAMAP-Rule:MF_01331_B] 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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