In vitro assembled yeast ribosome-nascent chain complexes (RNCs) containing a signal sequence in the nascent chain were immunopurified and reconstituted with the purified protein-conducting channel (PCC) of yeast endoplasmic reticulum, the Sec61 complex. A cryo-EM reconstruction of the RNC-Sec61 complex at 15.4 Å resolution shows a tRNA in the P site. Distinct rRNA elements and proteins of the large ribosomal subunit form four connections with the PCC across a gap of about 10-20 Å. Binding of the PCC influences the position of the highly dynamic rRNA expansion segment 27. The RNC-bound Sec61 complex has a compact appearance and was estimated to be a trimer. We propose a binary model of cotranslational translocation entailing only two basic functional states of the translating ribosome-channel complex.
CITATION STYLE
Beckmann, R., Spahn, C. M. T., Eswar, N., Helmers, J., Penczek, P. A., Sali, A., … Blobel, G. (2001). Architecture of the protein-conducting channel associated with the translating 80S ribosome. Cell, 107(3), 361–372. https://doi.org/10.1016/S0092-8674(01)00541-4
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