Journal of Biological Chemistry
Volume 285, Issue 47, 19 November 2010, Pages 36427-36433
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Cell Biology
BiP Modulates the Affinity of Its Co-chaperone ERj1 for Ribosomes*

https://doi.org/10.1074/jbc.M110.143263Get rights and content
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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.

Endoplasmic Reticulum (ER)
Membrane Proteins
Protein Translocation
Ribosomes
Surface Plasmon Resonance (SPR)
Chaperone
Hsp40
Hsp70

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*

This work was supported in part by grants from Homburger Forschungsförderungsprogramm (HOMFOR) and the Deutsche Forschungsgemeinschaft (FOR 967 and SFB530).

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1 and S2.

1

An Ellison Medical Foundation New Scholar in Aging. Supported by National Institutes of Health Grant R21 DK074650-01 and a pilot award from the Marion Bessin Liver Center.