PMID: 3771569Nov 15, 1986Paper

Kinetics of mitochondrial calcium transport. I. Characteristics of the sodium-independent calcium efflux mechanism of liver mitochondria.

The Journal of Biological Chemistry
D E Wingrove, T E Gunter

Abstract

The kinetics of sodium-independent calcium efflux from liver mitochondria has been studied over the range of calcium loads from 2 to 60 nmol/mg with emphasis on the lower portion of this range. A procedure has been developed through which mitochondria may be depleted of endogenous calcium (initially in the range of 6-10 nmol/mg following preparation) to values as low as 2 nmol/mg, without involving substrate depletion or de-energization. Mitochondria depleted of calcium by this technique are more resistant to the calcium-induced permeability transition than are those depleted by the older procedures and are therefore appropriate for the kinetics studies. Calcium depletion is necessary in studying the kinetics of sodium-independent calcium efflux in order to bring efflux to a rate considerably less than 50% of the saturation rate. The results of these studies show cooperativity with a Hill coefficient of 1.9 +/- 0.2. They have been fit to an equation representative either of a nonessential activation mechanism with a single transport site or of an Adair-Pauling mechanism with two transport sites. From the fit of the data to this equation, a Vmax of 1.2 +/- 0.1 nmol/mg/min and a concentration of half-maximal activity of 8.4 +/- 0...Continue Reading

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