title: Effect of denaturants on multisite and unisite ATP hydrolysis by bovine heart submitochondrial particles with and without inhibitor protein.
abstract: The effect of guanidinium hydrochloride (GdnHCl) on multisite and unisite ATPase activity by F0F1 of submitochondrial particles from bovine hearts was studied. In particles without control by the inhibitor protein, 50 mM GdnHCl inhibited multisite hydrolysis by about 85%; full inhibition required around 500 mM. In the range of 500-650 mM, GdnHCl enhanced the rate of unisite catalysis by promoting product release; it also increased the rate of hydrolysis of ATP bound to the catalytic site without GdnHCl. GdnHCl diminished the affinity of the enzyme for aurovertin. The effects of GdnHCl were irreversible. The results suggest that disruption of intersubunit contacts in F0F1 abolishes multisite hydrolysis and stimulates of unisite hydrolysis. Particles under control by the inhibitor protein were insensitive to concentrations of GdnHCl that induce the aforementioned alterations of F0F1 free of inhibitor protein, indicating that the protein stabilizes the global structure of particulate F1.
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70243, 04510 México, D. F., Mexico. apuyou@ifisiol.unam.mx
authors.forename: Marietta Tuena
authors.initials: MT
authors.lastname: de Gómez-Puyou
authors.forename: Lenin
authors.initials: L
authors.lastname: Domínguez-Ramírez
authors.forename: Gerardo
authors.initials: G
authors.lastname: Pérez-Hernández
authors.forename: Armando
authors.initials: A
authors.lastname: Gómez-Puyou
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D001313:Aurovertins / Q000737:chemistry; D002417:Cattle; D004789:Enzyme Activation; D019791:Guanidine / Q000737:chemistry*; D006868:Hydrolysis; D008929:Mitochondria, Heart / Q000201:enzymology*; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D013367:Submitochondrial Particles / Q000201:enzymology*; D014475:Uncoupling Agents / Q000737:chemistry; D000097795:ATPase Inhibitory Protein
chemical_list: D000255:Adenosine Triphosphate; D001313:Aurovertins; D019791:Guanidine; D011506:Proteins; D006180:Proton-Translocating ATPases; D014475:Uncoupling Agents; D000097795:ATPase Inhibitory Protein