title: BiP modulates the affinity of its co-chaperone ERj1 for ribosomes.
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.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Benedix
authors.forename: Patrick
authors.initials: P
authors.lastname: Lajoie
authors.forename: Himjyot
authors.initials: H
authors.lastname: Jaiswal
authors.forename: Carsten
authors.initials: C
authors.lastname: Burgard
authors.forename: Markus
authors.initials: M
authors.lastname: Greiner
authors.forename: Richard
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Sabine
authors.initials: S
authors.lastname: Rospert
authors.forename: Erik L
authors.initials: EL
authors.lastname: Snapp
authors.forename: Johanna
authors.initials: J
authors.lastname: Dudek
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones; D009842:Oligopeptides / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism; D014176:Protein Biosynthesis; D016601:RNA-Binding Proteins; D012270:Ribosomes / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: C539791:Bax-inhibiting peptide, BIP; D004268:DNA-Binding Proteins; C414672:DNAJC2 protein, human; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D009842:Oligopeptides; D015513:Oncogene Proteins; D016601:RNA-Binding Proteins