Spontaneous modification of the oxoglutarate translocator in vivo.

In studying the oxoglutarate translocator of rat-heart mitochondria over many years, we have observed an unexpected decrease in its efficiency. It has been divided by 2.48 +/- 0.

Conformational changes and possible structure of the oxoglutarate translocator of rat-heart mitochondria revealed by the kinetic study of malate and oxoglutarate uptake.

Initial rates of the exchanges [14C]malateout:malatein, ([14C]oxoglutarate + malate)out:malatein and ([14C]malate + oxoglutarate)out:malatein catalysed by the oxoglutarate carrier of rat-heart mitochondria have been studied under conditions where internal and external substrates may be varied. It is shown that contrary to external oxoglutarate which induces a conformational change of the translocator subunit to which it binds, external malate does not induce conformational changes during its binding and is a Michaelian substrate. The study of the effect of external malate on the rate of oxoglutarate uptake shows that external malate and external oxoglutarate are competitive.

Kinetic mechanism of the exchanges catalysed by the adenine-nucleotide carrier.

Initial rates of the exchange ADPin/ADPout catalysed by the adenine-nucleotide carrier of rat-heart mitochondria have been studied under conditions where internal and external ADP may be varied. The initial rate was measured within 1 s by the carboxyatractyloside-stop method, using a rapid-mixing technique. The double-reciprocal plots v0(-1) versus [ADP]out-1 at different internal-ADP concentrations and v0(-1) versus [ADP]in-1 at different external-ADP concentrations exhibit straight-line relationships having a common point of intersection on the axis of ordinates.

Kinetic and binding properties of the oxoglutarate translocator of rat-heart mitochondria.

The kinetic study of the oxoglutarateout/malatein exchange through the inner mitochondrial membrane of rat-heart mitochondria has been compelted and extended to higher external-oxoglutarate and to lower internal-malate concentrations. It has been found that the external oxoglutarate inhibits the exchange at high concentration. This excess-substrate inhibition is preceded by four jumps.

Evidence for cooperative effects in the exchange reaction catalysed by the oxoglutarate translocator of rat-heart mitochondria.

The initial rates of the exchange external oxoglutarate/internal malate through the inner membrane of rat-heart mitochondria, for various concentrations of the two substrates, have been reinvestigated for an extended range of concentrations of the external oxoglutarate. This has been made possible by use of the inhibitor-stop technique that allows 100 times smaller incubation times than the centrifugation-stop technique used previously. Under the experimental conditions the uptake of the external-labelled oxoglutarate into the mitochondrial-matrix space is mediated by the oxoglutarate translocator performing a ono-to-one exchange of the anions oxoglutarate (external) and malate (internal).