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Effects of Naturally Occurring Polyols and Urea on Mitochondrial F 0 F 1 ATPase

2000; De Gruyter; Volume: 55; Issue: 5-6 Linguagem: Inglês

10.1515/znc-2000-5-614

1865-7125

Adriana dos Passos Lemos, Carlos E. Peres-Sampaio, Horácio Guimarães-Motta, Jerson L. Silva, José Roberto Meyer‐Fernandes,

Mitochondrial Function and Pathology

We show that urea inhibits the ATPase activity of MgATP submitochondrial particles (MgATP-SMP) with Ki = 0.7 м, probably as a result of direct interaction with the structure of F 0 F 1 -ATPase. Counteracting compounds (sorbitol, mannitol or inositol), despite slightly (10-20% ) inhibiting the ATPase activity, also protect the F 0 F 1 ATPase against denaturation by urea. However, this protection was only observed at low urea concentrations (less than 1.5 м ) , and in the presence of three polyols, the K i for urea shift from 0.7 м to 1.2 м. Urea also increases the initial activation rate of latent MgATP-SMP in a dose-dependent-manner. However, when the particles (0.5 mg/ml) were preincubated in the presence of 1 м , 2 м or 3 м urea, a decrease in the activation level occurred after 1 h, 30 and 10 min, respectively. At high MgATP-SMP concentration (3 mg/ml) a decrease in activation was observed after 2 h, 1 h and 20 min, respectively. These data indicate that the effect of urea on the activation of MgATP-SMP depends on time, urea and protein concentrations. It was also observed that polyols suppress the activation of latent MgATP-SMP in a dose-dependent manner, and protect the particles against urea denaturation during activation. We suppose that a decrease in membrane mobility promoted by interactions of polyols with phospholipids around the F 0 F 1 ATPase may also increase the compactation of protein structure, explaining the inhibition of natural inhibitor protein of ATPase (IF 1 ) release and the activation of the enzyme.