title: GTP hydrolysis is essential for protein import into the mitochondrial matrix.
abstract: Protein import into the innermost compartment of mitochondria (the matrix) requires a membrane potential (delta psi) across the inner membrane, as well as ATP-dependent interactions with chaperones in the matrix and cytosol. The role of nucleoside triphosphates other than ATP during import into the matrix, however, remains to be determined. Import of urea-denatured precursors does not require cytosolic chaperones. We have therefore used a purified and urea-denatured preprotein in our import assays to bypass the requirement of external ATP. Using this modified system, we demonstrate that GTP stimulates protein import into the matrix; the stimulatory effect is directly mediated by GTP hydrolysis and does not result from conversion of GTP to ATP. Both external GTP and matrix ATP are necessary; neither one can substitute for the other if efficient import is to be achieved. These results suggest a "push-pull" mechanism of import, which may be common to other post-translational translocation pathways.
authors.affiliation: Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085, USA.
authors.forename: N B
authors.initials: NB
authors.lastname: Sepuri
authors.forename: N
authors.initials: N
authors.lastname: Schülke
authors.forename: D
authors.initials: D
authors.lastname: Pain
mesh_terms: D050842:1-Pyrroline-5-Carboxylate Dehydrogenase; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D003600:Cytosol / Q000378:metabolism; D004926:Escherichia coli; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism*; D012441:Saccharomyces cerevisiae
chemical_list: D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D050842:1-Pyrroline-5-Carboxylate Dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors