1BUP

T13S MUTANT OF BOVINE 70 KILODALTON HEAT SHOCK PROTEIN

Summary for 1BUP

• Entry DOI: 10.2210/pdb1bup/pdb
• Descriptor: PROTEIN (70 KILODALTON HEAT SHOCK PROTEIN), MAGNESIUM ION, POTASSIUM ION, ... (7 entities in total)
• Functional Keywords: hydrolase (acting on acid anhydrides), molecular chaperone, atpase, hydrolase
• Biological source: Bos taurus (cattle)
• Total number of polymer chains: 1
• Total formula weight: 43194.59

Authors

Sousa, M.C.,Mckay, D.B. (deposition date: 1998-09-03, release date: 1998-09-09, Last modification date: 2023-08-09)

Primary citation

Sousa, M.C.,McKay, D.B.
The hydroxyl of threonine 13 of the bovine 70-kDa heat shock cognate protein is essential for transducing the ATP-induced conformational change.
Biochemistry, 37:15392-15399, 1998

PubMed Abstract: 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.

PubMed: 9799500
DOI: 10.1021/bi981510x

Experimental method

X-RAY DIFFRACTION (1.7 Å)