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Solution structure of the SBDbeta domain of yeast Ssa1
Structural highlights
FunctionHSP71_YEAST May play a role in the transport of polypeptides both across the mitochondrial membranes and into the endoplasmic reticulum. A functional difference between SSA1 and SSA2 proteins is expected. SSA1 can participate in the ATP-dependent disassembly of clathrin-coated vesicles.[1] Publication Abstract from PubMedThe allosteric coupling of the highly conserved nucleotide- and substrate-binding domains of Hsp70 has been studied intensively. In contrast, the role of the disordered, highly variable C-terminal region of Hsp70 remains unclear. In many eukaryotic Hsp70s, the extreme C-terminal EEVD motif binds to tetratricopeptide-repeat domains of Hsp70 co-chaperones. Here, we discovered that the TVEEVD sequence of Saccharomyces cerevisiae cytoplasmic Hsp70 (Ssa1) functions as a SUMO-interacting motif. A second C-terminal motif of ~15 amino acids between the alpha-helical lid and the extreme C terminus, previously identified in bacterial and eukaryotic organellar Hsp70s, is known to enhance chaperone function by transiently interacting with folding clients. Using structural analysis, interaction studies, fibril formation assays, and in vivo functional assays, we investigated the individual contributions of the alpha-helical bundle and the C-terminal disordered region of Ssa1 in the inhibition of fibril formation of the prion protein Ure2. Our results revealed that although the alpha-helical bundle of the Ssa1 substrate-binding domain (SBDalpha) does not directly bind to Ure2, the SBDalpha enhances the ability of Hsp70 to inhibit fibril formation. We found that a 20-residue C-terminal motif in Ssa1, containing GGAP and GGAP-like tetra-peptide repeats, can directly bind to Ure2, the Hsp40 co-chaperone Ydj1, and alpha-synuclein, but not to the SUMO-like protein SMT3 or BSA. Deletion or substitution of the Ssa1 GGAP motif impaired yeast cell tolerance to temperature and cell wall damage stress. This study highlights that the C-terminal GGAP motif of Hsp70 is important for substrate recognition and mediation of the heat shock response. The C-terminal GGAP motif of Hsp70 mediates substrate recognition and stress response in yeast.,Gong W, Hu W, Xu L, Wu H, Wu S, Zhang H, Wang J, Jones GW, Perrett S J Biol Chem. 2018 Sep 18. pii: RA118.002691. doi: 10.1074/jbc.RA118.002691. PMID:30228181[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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