Effects of Naturally Occurring Polyols and Urea on Mitochondrial F₀F₁ATPase

Abstract

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 F0F1-ATPase. Counteracting compounds (sorbitol, mannitol or inositol), despite slightly (10-20% ) inhibiting the ATPase activity, also protect the F0F1 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 Ki 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 F0F1 ATPase may also increase the compactation of protein structure, explaining the inhibition of natural inhibitor protein of ATPase (IF1) release and the activation of the enzyme.

A current perspective on the compensatory effects of urea and methylamine on protein stability and function

“…In another development, glutamate has been shown to counteract the denaturing effects of urea on glutaminyl-tRNA synthetase from Escherichia coli (Mandal et al, 2003). This counteraction behaviour has been hypothesised to be due to the effect of (Lemos et al, 2000). In addition, Trehalose has also been found to strongly offset the denaturing effects of urea on chymotrypsinogen (Kumar et al, 2010).…”

Ecto-ATPase activity on the surface of Trypanosoma cruzi and its possible role in the parasite?host cell interaction

“…Mg 2+ -dependent ecto-ATPase activity was calculated from the total activity, measured in the presence of 5 mM MgCl 2 , minus the basal activity, measured in the absence of MgCl 2 . ATPase activity was determined by measuring the hydrolysis of [c-32 P]ATP (10 4 Bq/nmol ATP; Lemos et al 2000). The experiments were started by the addition of living cells and terminated by the addition of 1 ml of a cold mixture containing 200 mg charcoal in 1 M HCl.…”