title: Role of mitochondrial GrpE and phosphate in the ATPase cycle of matrix Hsp70.
abstract: 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.
authors.affiliation: Institut für Biochemie und Molekularbiologie, Universität Freiburg, Germany.
authors.forename: P J
authors.initials: PJ
authors.lastname: Dekker
authors.forename: N
authors.initials: N
authors.lastname: Pfanner
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins; D006868:Hydrolysis; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D018832:Molecular Chaperones; D010710:Phosphates / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C086039:MGE1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D018832:Molecular Chaperones; D010710:Phosphates; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases