1s3x
From Proteopedia
The crystal structure of the human Hsp70 ATPase domain
Structural highlights
FunctionHS71A_HUMAN In cooperation with other chaperones, Hsp70s stabilize preexistent proteins against aggregation and mediate the folding of newly translated polypeptides in the cytosol as well as within organelles. These chaperones participate in all these processes through their ability to recognize nonnative conformations of other proteins. They bind extended peptide segments with a net hydrophobic character exposed by polypeptides during translation and membrane translocation, or following stress-induced damage. In case of rotavirus A infection, serves as a post-attachment receptor for the virus to facilitate entry into the cell. Essential for STUB1-mediated ubiquitination and degradation of FOXP3 in regulatory T-cells (Treg) during inflammation (PubMed:23973223).[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: The 70 kDa heat shock proteins (Hsp70) are a family of molecular chaperones, which promote protein folding and participate in many cellular functions. The Hsp70 chaperones are composed of two major domains. The N-terminal ATPase domain binds to and hydrolyzes ATP, whereas the C-terminal domain is required for polypeptide binding. Cooperation of both domains is needed for protein folding. The crystal structure of bovine Hsc70 ATPase domain (bATPase) has been determined and, more recently, the crystal structure of the peptide-binding domain of a related chaperone, DnaK, in complex with peptide substrate has been obtained. The molecular chaperone activity and conformational switch are functionally linked with ATP hydrolysis. A high-resolution structure of the ATPase domain is required to provide an understanding of the mechanism of ATP hydrolysis and how it affects communication between C- and N-terminal domains. RESULTS: The crystal structure of the human Hsp70 ATPase domain (hATPase) has been determined and refined at 1. 84 A, using synchrotron radiation at 120K. Two calcium sites were identified: the first calcium binds within the catalytic pocket, bridging ADP and inorganic phosphate, and the second calcium is tightly coordinated on the protein surface by Glu231, Asp232 and the carbonyl of His227. Overall, the structure of hATPase is similar to bATPase. Differences between them are found in the loops, the sites of amino acid substitution and the calcium-binding sites. Human Hsp70 chaperone is phosphorylated in vitro in the presence of divalent ions, calcium being the most effective. CONCLUSIONS: The structural similarity of hATPase and bATPase and the sequence similarity within the Hsp70 chaperone family suggest a universal mechanism of ATP hydrolysis among all Hsp70 molecular chaperones. Two calcium ions have been found in the hATPase structure. One corresponds to the magnesium site in bATPase and appears to be important for ATP hydrolysis and in vitro phosphorylation. Local changes in protein structure as a result of calcium binding may facilitate phosphorylation. A small, but significant, movement of metal ions and sidechains could position catalytically important threonine residues for phosphorylation. The second calcium site represents a new calcium-binding motif that can play a role in the stabilization of protein structure. We discuss how the information about catalytic events in the active site could be transmitted to the peptide-binding domain. Human Hsp70 molecular chaperone binds two calcium ions within the ATPase domain.,Sriram M, Osipiuk J, Freeman B, Morimoto R, Joachimiak A Structure. 1997 Mar 15;5(3):403-14. PMID:9083109[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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