BiP Modulates the Affinity of Its Co-chaperone ERj1 for Ribosomes |
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| Authors: | Julia Benedix Patrick Lajoie Himjyot Jaiswal Carsten Burgard Markus Greiner Richard Zimmermann Sabine Rospert Erik L Snapp Johanna Dudek |
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| Institution: | From the ‡Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.;the §Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, and ;the ¶Institute of Biochemistry and Molecular Biology and Center for Biological Signaling Studies, University of Freiburg, 79104 Freiburg, Germany |
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| Abstract: | Ribosomes synthesizing secretory and membrane proteins are bound to the endoplasmic reticulum (ER) membrane and attach to ribosome-associated membrane proteins such as the Sec61 complex, which forms the protein-conducting channel in the membrane. The ER membrane-resident Hsp40 protein ERj1 was characterized as being able to recruit BiP to ribosomes in solution and to regulate protein synthesis in a BiP-dependent manner. Here, we show that ERj1 and Sec61 are associated with ribosomes at the ER of human cells and that the binding of ERj1 to ribosomes occurs with a binding constant in the picomolar range and is prevented by pretreatment of ribosomes with RNase. However, the affinity of ERj1 for ribosomes dramatically changes upon binding of BiP. This modulation by BiP may be responsible for the dual role of ERj1 at the ribosome, i.e. acting as a recruiting factor for BiP and regulating translation. |
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| Keywords: | Endoplasmic Reticulum (ER) Membrane Proteins Protein Translocation Ribosomes Surface Plasmon Resonance (SPR) Chaperone Hsp40 Hsp70 |
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