Citrate uniport by the mitochondrial tricarboxylate carrier: a basis for a new hypothesis for the transport mechanism.

摘要: The tricarboxylate transport system located in the inner mitochondrial membrane was studied as an isolated protein reconstituted proteoliposomes. effects on of citrate by various reagents, specific for different aminoacid residues, were analyzed. In group SH it found that N-ethylmaleimide is irreversible inhibitor citrate–citrate exchange, while HgCl2 and mercurial mersalyl cause a rapid unidirectional efflux from liposomes. It demonstrated NEM mercurials act groups. Dithioerythritol not able to reverse effect unless another reagent, pyridoxalphosphate, present. Pyridoxalphosphate itself, reagent NH2 effective exchange transport, measured both influx efflux, but has no mercurial-induced efflux. same behavior observed with diethylpyrocarbonate, histidine tyrosine residues. Interestingly, slow basic internal citrate, absence countersubstrate, Because inhibited reagents acting process, deduced catalyzed carrier. ability carrier perform uniport substrate suggests presence single binding site protein. A preliminary kinetic approach indicates such model compatible this theory.