title: Vacuolar ATPases, like F1,F0-ATPases, show a strong dependence of the reaction velocity on the binding of more than one ATP per enzyme.
abstract: Recent studies with vacuolar ATPases have shown that multiple copies catalytic subunits are present and that these have definite sequence homology with catalytic subunits of the F1,F0-ATPases. Experiments are reported that assess whether the vacuolar ATPases may have the unusual catalytic cooperativity with sequential catalytic site participation as in the binding change mechanism for the F1,F0-ATPases. The extent of reversal of bound ATP hydrolysis to bound ADP and Pi as medium ATP concentration was lowered was determined by 18O-exchange measurements for yeast and neurospora vacuolar ATPases. The results show a pronounced increase in the extent of water oxygen incorporation into the Pi formed as ATP concentration is decreased to the micromolar range. The F1,F0-ATPase from neurospora mitochondria showed an even more pronounced modulation, similar to that of other F1-type ATPases. The vacuolar ATPases thus appear to have a catalytic mechanism quite analogous to that of the F1,F0-ATPases.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles 90024-1570.
authors.forename: V N
authors.initials: VN
authors.lastname: Kasho
authors.forename: P D
authors.initials: PD
authors.lastname: Boyer
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001665:Binding Sites; D007700:Kinetics; D046911:Macromolecular Substances; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology*; D010103:Oxygen Isotopes; D011485:Protein Binding; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D014617:Vacuoles / Q000201:enzymology*
chemical_list: D046911:Macromolecular Substances; D010103:Oxygen Isotopes; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases