6s0k
Ribosome nascent chain in complex with SecA
Structural highlights
FunctionRL19_ECOLI This protein is located at the 30S-50S ribosomal subunit interface. In the 70S ribosome (PubMed:12809609) it has been modeled to make two contacts with the 16S rRNA of the 30S subunit forming part of bridges B6 and B8. In the 3.5 A resolved structures (PubMed:16272117) L14 and L19 interact and together make contact with the 16S rRNA. The protein conformation is quite different between the 50S and 70S structures, which may be necessary for translocation.[HAMAP-Rule:MF_00402] Publication Abstract from PubMedCotranslational protein targeting is a conserved process for membrane protein biogenesis. In Escherichia coli, the essential ATPase SecA was found to cotranslationally target a subset of nascent membrane proteins to the SecYEG translocase at the plasma membrane. The molecular mechanism of this pathway remains unclear. Here we use biochemical and cryoelectron microscopy analyses to show that the amino-terminal amphipathic helix of SecA and the ribosomal protein uL23 form a composite binding site for the transmembrane domain (TMD) on the nascent protein. This binding mode further enables recognition of charged residues flanking the nascent TMD and thus explains the specificity of SecA recognition. Finally, we show that membrane-embedded SecYEG promotes handover of the translating ribosome from SecA to the translocase via a concerted mechanism. Our work provides a molecular description of the SecA-mediated cotranslational targeting pathway and demonstrates an unprecedented role of the ribosome in shielding nascent TMDs. The molecular mechanism of cotranslational membrane protein recognition and targeting by SecA.,Wang S, Jomaa A, Jaskolowski M, Yang CI, Ban N, Shan SO Nat Struct Mol Biol. 2019 Sep 30. pii: 10.1038/s41594-019-0297-8. doi:, 10.1038/s41594-019-0297-8. PMID:31570874[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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