ATPase domain of Hsp70 exhibits intrinsic ATP-ADP exchange activity |
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Authors: | Yubin Mao Aihua Deng Ning Qu Xueji Wu |
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Affiliation: | (1) Medical College, Xiamen University-National University of Singapore Laboratory of Biomedical Sciences, Xiamen University, Daxue Road 168, Xiamen, 361005, China;(2) School of Life Sciences, Xiamen University-National University of Singapore Laboratory of Biomedical Sciences, Xiamen University, Daxue Road 168, Xiamen, 361005, China |
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Abstract: | The chaperone activity of Hsp70 in protein folding and its conformational switching are regulated through the hydrolysis of ATP and the ATP-ADP exchange cycle. It was reported that, in the presence of physiological concentrations of ATP (approximately 5 mM) and ADP (approximately 0.5 mM), Hsp70 catalyzes ATP-ADP exchange through transfer of gamma-phosphate between ATP and ADP, via an autophosphorylated intermediate, whereas it only catalyzes the hydrolysis of ATP in the absence of ADP. To clarify the functional domain of the ATP-ADP exchange activity of Hsp70, we isolated the 44-kD ATPase domain of Hsp70 after limited proteolysis with alpha-chymotrypsin (EC 3.4.21.1). The possibility of ATP-ADP exchange activity of a contaminating nucleoside diphosphate kinase (EC 2.7.4.6) was monitored throughout the experiments. The purified 44-kD ATPase domain exhibited intrinsic ATP-ADP exchange by catalyzing the transfer of gamma-phosphate between ATP and ADP with acid-stable autophosphorylation at Thr204. |
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Keywords: | ATP-ADP exchange ATPase domain autophosphorylation Hsp70 |
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