2bup
T13G MUTANT OF THE ATPASE FRAGMENT OF BOVINE HSC70
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OverviewOverview
The mechanism by which ATP binding transduces a conformational change in, 70-kDa heat shock proteins that results in release of bound peptides, remains obscure. Wei and Hendershot demonstrated that mutating Thr37 of, hamster BiP to glycine impeded the ATP-induced conformational change, as, monitored by proteolysis [(1995) J. Biol. Chem. 270, 26670-26676]. We have, mutated the equivalent resitude of the bovine heat shock cognate protein, (Hsc70), Thr13, to serine, valine, and glycine. Solution small-angle X-ray, scattering experiments on a 60-kDa fragment of Hsc70 show that ATP binding, induces a conformational change in the T13S mutant but not the T13V or, T13G mutants. The kinetics of ATP-induced tryptophan fluorescence, intensity changes in the 60-kDa proteins is biphasic for the T13S mutant, but monophasic for T13V or T13G, consistent with a conformational change, following initial ATP binding in the T13S mutant but not the other two., Crystallographic structures of the ATPase fragments of the T13S and T13G, mutants at 1.7 A resolution show that the mutations do not disrupt the ATP, binding site and that the serine hydroxyl mimics the threonine hydroxyl in, the wild-type structure. We conclude that the hydroxyl of Thr13 is, essential for coupling ATP binding to a conformational change in Hsc70., Molecular modeling suggests this may result from the threonine hydroxyl, hydrogen-bonding to a gamma-phosphate oxygen of ATP, thereby inducing a, structural shift within the ATPase domain that couples to its interactions, with the peptide binding domain.
About this StructureAbout this Structure
2BUP is a Single protein structure of sequence from Bos taurus with PO4, MG, K, CL, ADP and ATP as ligands. Full crystallographic information is available from OCA.
ReferenceReference
The hydroxyl of threonine 13 of the bovine 70-kDa heat shock cognate protein is essential for transducing the ATP-induced conformational change., Sousa MC, McKay DB, Biochemistry. 1998 Nov 3;37(44):15392-9. PMID:9799500
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