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Role Of Sec61alpha In The Regulated Transfer Of The Ribosome-Nascent Chain Complex From The Signal Recognition Particle To The Translocation Channel, Weiqun Song, David Raden, Elisabet Mandon, Reid Gilmore
Role Of Sec61alpha In The Regulated Transfer Of The Ribosome-Nascent Chain Complex From The Signal Recognition Particle To The Translocation Channel, Weiqun Song, David Raden, Elisabet Mandon, Reid Gilmore
Elisabet Mandon
Targeting of ribosome-nascent chain complexes to the translocon in the endoplasmic reticulum is mediated by the concerted action of the signal recognition particle (SRP) and the SRP receptor (SR). Ribosome-stripped microsomes were digested with proteases to sever cytoplasmic domains of SRalpha, SRbeta, TRAM, and the Sec61 complex. We characterized protein translocation intermediates that accumulate when Sec61alpha or SRbeta is inactivated by proteolysis. In the absence of a functional Sec61 complex, dissociation of SRP54 from the signal sequence is blocked. Experiments using SR proteoliposomes confirmed the assembly of a membrane-bound posttargeting intermediate. These results strongly suggest that the Sec61 complex regulates …
An Interaction Between The Srp Receptor And The Translocon Is Critical During Cotranslational Protein Translocation, Ying Jiang, Zhiliang Cheng, Elisabet Mandon, Reid Gilmore
An Interaction Between The Srp Receptor And The Translocon Is Critical During Cotranslational Protein Translocation, Ying Jiang, Zhiliang Cheng, Elisabet Mandon, Reid Gilmore
Elisabet Mandon
The signal recognition particle (SRP)-dependent targeting pathway facilitates rapid, efficient delivery of the ribosome-nascent chain complex (RNC) to the protein translocation channel. We test whether the SRP receptor (SR) locates a vacant protein translocation channel by interacting with the yeast Sec61 and Ssh1 translocons. Surprisingly, the slow growth and cotranslational translocation defects caused by deletion of the transmembrane (TM) span of yeast SRbeta (SRbeta-DeltaTM) are exaggerated when the SSH1 gene is disrupted. Disruption of the SBH2 gene, which encodes the beta subunit of the Ssh1p complex, likewise causes a growth defect when combined with SRbeta-DeltaTM. Cotranslational translocation defects in the …
Identification Of Cytoplasmic Residues Of Sec61p Involved In Ribosome Binding And Cotranslational Translocation, Zhiliang Cheng, Ying Jiang, Elisabet Mandon, Reid Gilmore
Identification Of Cytoplasmic Residues Of Sec61p Involved In Ribosome Binding And Cotranslational Translocation, Zhiliang Cheng, Ying Jiang, Elisabet Mandon, Reid Gilmore
Elisabet Mandon
The cytoplasmic surface of Sec61p is the binding site for the ribosome and has been proposed to interact with the signal recognition particle receptor during targeting of the ribosome nascent chain complex to the translocation channel. Point mutations in cytoplasmic loops six (L6) and eight (L8) of yeast Sec61p cause reductions in growth rates and defects in the translocation of nascent polypeptides that use the cotranslational translocation pathway. Sec61 heterotrimers isolated from the L8 sec61 mutants have a greatly reduced affinity for 80S ribosomes. Cytoplasmic accumulation of protein precursors demonstrates that the initial contact between the large ribosomal subunit and …