title: Crystal structure of yeast Sis1 peptide-binding fragment and Hsp70 Ssa1 C-terminal complex.
abstract: Heat shock protein (Hsp) 40 facilitates the critical role of Hsp70 in a number of cellular processes such as protein folding, assembly, degradation and translocation in vivo. Hsp40 and Hsp70 stay in close contact to achieve these diverse functions. The conserved C-terminal EEVD motif in Hsp70 has been shown to regulate Hsp40-Hsp70 interaction by an unknown mechanism. Here, we provide a structural basis for this regulation by determining the crystal structure of yeast Hsp40 Sis1 peptide-binding fragment complexed with the Hsp70 Ssa1 C-terminal. The Ssa1 extreme C-terminal eight residues, G634PTVEEVD641, form a beta-strand with the domain I of Sis1 peptide-binding fragment. Surprisingly, the Ssa1 C-terminal binds Sis1 at the site where Sis1 interacts with the non-native polypeptides. The negatively charged residues within the EEVD motif in Ssa1 C-terminal form extensive charge-charge interactions with the positively charged residues in Sis1. The structure-based mutagenesis data support the structural observations.
authors.affiliation: Department of Cell Biology, Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Brimingham, AL 35294-0005, USA.
authors.forename: Jingzhi
authors.initials: J
authors.lastname: Li
authors.forename: Yunkun
authors.initials: Y
authors.lastname: Wu
authors.forename: Xinguo
authors.initials: X
authors.lastname: Qian
authors.forename: Bingdong
authors.initials: B
authors.lastname: Sha
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D021122:Protein Subunits; C070320:SIS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C095973:SSA1 protein, S cerevisiae