Crystal structure of Hsc20, a J-type Co-chaperone from Escherichia coli.
Hsc20 is a 20 kDa J-protein that regulates the ATPase activity and peptide-binding specificity of Hsc66, an hsp70-class molecular chaperone. We report herein the crystal structure of Hsc20 from Escherichia coli determined to a resolution of 1.8 A using a combination of single isomorphous replacement (SIR) and multi-wavelength anomalous diffraction (MAD). The overall structure of Hsc20 consists of two distinct domains, an N-terminal J-domain containing residues 1-75 connected by a short loop to a C-terminal domain containing residues 84-171. The structure of the J-domain, involved in interactions with Hsc66, resembles the alpha-topology of J-domain fragments of Escherichia coli DnaJ and human Hdj1 previously determined by solution NMR methods. The C-terminal domain, implicated in binding and targeting proteins to Hsc66, consists of a three-helix bundle in which two helices comprise an anti-parallel coiled-coil. The two domains make contact through an extensive hydrophobic interface ( approximately 650 A(2)) suggesting that their relative orientations are fixed. Thus, Hsc20, in addition to its role in the regulation of the ATPase activity of Hsc66, may also function as a rigid scaffold to facilitate positioning of the protein substrates targeted to Hsc66.
Cupp-Vickery
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Department of Chemistry and Biochemistry, California State University, Fullerton, CA 92834, USA. lvickery@uci.edu
Vickery
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D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites; D017124:Conserved Sequence / Q000235:genetics; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
C494647:DNAJB1 protein, human; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C490651:HSCB protein, human; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C095453:HscB protein, E coli; D018832:Molecular Chaperones; D003545:Cysteine