title: J domain co-chaperone specificity defines the role of BiP during protein translocation.
abstract: Hsp70 chaperones can potentially interact with one of several J domain-containing Hsp40 co-chaperones to regulate distinct cellular processes. However, features within Hsp70s that determine Hsp40 specificity are undefined. To investigate this question, we introduced mutations into the ER-lumenal Hsp70, BiP/Kar2p, and found that an R217A substitution in the J domain-interacting surface of BiP compromised the physical and functional interaction with Sec63p, an Hsp40 required for ER translocation. In contrast, interaction with Jem1p, an Hsp40 required for ER-associated degradation, was unaffected. Moreover, yeast expressing R217A BiP exhibited defects in translocation but not in ER-associated degradation. Finally, the genetic interactions of the R217A BiP mutant were found to correlate with those of known translocation mutants. Together, our results indicate that residues within the Hsp70 J domain-interacting surface help confer Hsp40 specificity, in turn influencing distinct chaperone-mediated cellular activities.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Shruthi S
authors.initials: SS
authors.lastname: Vembar
authors.forename: Martin C
authors.initials: MC
authors.lastname: Jonikas
authors.forename: Linda M
authors.initials: LM
authors.lastname: Hendershot
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Weissman
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Brodsky
mesh_terms: D004721:Endoplasmic Reticulum / Q000473:pathology; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013312:Stress, Physiological; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C060153:KAR2 protein, yeast; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D050505:Mutant Proteins; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins