biostudies-literatureYang CINational Institutes of HealthNIGMS NIH HHSNIGMS167535https://www.ebi.ac.uk/biostudies/studies/S-EPMC9126151biostudies-literatureUnknown434(9)Numerous proteins initiate their folding, localization, and modifications early during translation, and emerging data show that the ribosome actively participates in diverse protein biogenesis pathways. Here we show that the ribosome imposes an additional layer of substrate selection during N-terminal methionine excision (NME), an essential protein modification in bacteria. Biochemical analyses show that cotranslational NME is exquisitely sensitive to a hydrophobic signal sequence or transmembrane domain near the N terminus of the nascent polypeptide. The ability of the nascent chain to access the active site of NME enzymes dictates NME efficiency, which is inhibited by confinement of the nascent chain on the ribosome surface and exacerbated by signal recognition particle. In vivo measuremJournal of molecular biologyRibosome-nascent Chain Interaction Regulates N-terminal Protein Modification.PMC9126151R35 GM136321Yang CIKim JShan SOfalseRibosome-nascent Chain Interaction Regulates N-terminal Protein Modification.Numerous proteins initiate their folding, localization, and modifications early during translation, and emerging data show that the ribosome actively participates in diverse protein biogenesis pathways. Here we show that the ribosome imposes an additional layer of substrate selection during N-terminal methionine excision (NME), an essential protein modification in bacteria. Biochemical analyses show that cotranslational NME is exquisitely sensitive to a hydrophobic signal sequence or transmembrane domain near the N terminus of the nascent polypeptide. The ability of the nascent chain to access the active site of NME enzymes dictates NME efficiency, which is inhibited by confinement of the nascent chain on the ribosome surface and exacerbated by signal recognition particle. In vivo measurem2022-01-01T00:00:00Z2022 May2025-04-22T18:29:54.429Z2025-04-06T02:27:30.74ZS-EPMC91261513527847710.1016/j.jmb.2022.167535