Dekker P J, Pfanner N
Institut für Biochemie und Molekularbiologie, Universität Freiburg, Germany.
J Mol Biol. 1997 Jul 18;270(3):321-7. doi: 10.1006/jmbi.1997.1131.
The yeast mitochondrial GrpE homologue, Mge1, assists matrix Hsp70 in both protein translocation across the mitochondrial membranes and subsequent protein folding. We expressed mtHsp70 and Mge1 in Escherichia coli and analyzed their function in the ATP hydrolysis cycle. Mge1 stimulates ATP hydrolysis by mtHsp70 about twofold. Addition of inorganic phosphate inhibits ATP hydrolysis by preventing ADP release from mtHsp70. Mge1 has no direct effect on gamma-phosphate release from mtHsp70, yet indirectly relieves the phosphate inhibition by stimulating ADP release. We conclude that Mge1 promotes the ATPase cycle of mtHsp70 by increasing the rate of ADP release. ATP then rapidly binds to mtHsp70 such that the total amount of mtHsp70-bound nucleotide is not changed by Mge1.
酵母线粒体中的GrpE同源物Mge1，在蛋白质跨线粒体膜转运及随后的蛋白质折叠过程中协助基质Hsp70发挥作用。我们在大肠杆菌中表达了线粒体Hsp70（mtHsp70）和Mge1，并分析了它们在ATP水解循环中的功能。Mge1可刺激mtHsp70的ATP水解约两倍。添加无机磷酸盐可通过阻止ADP从mtHsp70释放来抑制ATP水解。Mge1对mtHsp70的γ-磷酸释放没有直接影响，但通过刺激ADP释放间接缓解了磷酸盐抑制作用。我们得出结论，Mge1通过提高ADP释放速率来促进mtHsp70的ATP酶循环。然后ATP迅速与mtHsp70结合，使得mtHsp70结合的核苷酸总量不会因Mge1而改变。
