'''T13G MUTANT OF THE ATPASE FRAGMENT OF BOVINE HSC70'''
===T13G MUTANT OF THE ATPASE FRAGMENT OF BOVINE HSC70===
==Overview==
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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.
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==About this Structure==
==About this Structure==
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[[Category: Atpase]]
[[Category: Atpase]]
[[Category: Molecular chaperone]]
[[Category: Molecular chaperone]]
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Revision as of 04:30, 29 July 2008
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2BUP is a Single protein structure of sequence from Bos taurus. Full crystallographic information is available from OCA.
Reference
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
