The mitochondrial oxoglutarate carrier: from identification to mechanism.
The 2-oxoglutarate carrier (OGC) belongs to the mitochondrial carrier protein family whose members are responsible for the exchange of metabolites, cofactors and nucleotides between the cytoplasm and mitochondrial matrix. Initially, OGC was characterized by determining substrate specificity, kinetic parameters of transport, inhibitors and molecular probes that form covalent bonds with specific residues. It was shown that OGC specifically transports oxoglutarate and certain carboxylic acids. The substrate specificity combination of OGC is unique, although many of its substrates are also transported by other mitochondrial carriers. The abundant recombinant expression of bovine OGC in Escherichia coli and its ability to functionally reconstitute into proteoliposomes made it possible to deduce the individual contribution of each and every residue of OGC to the transport activity by a complete set of cys-scanning mutants. These studies give experimental support for a substrate binding site constituted by three major contact points on the even-numbered α-helices and identifies other residues as important for transport function through their crucial positions in the structure for conserved interactions and the conformational changes of the carrier during the transport cycle. The results of these investigations have led to utilize OGC as a model protein for understanding the transport mechanism of mitochondrial carriers.
Department of Biosciences, Biotechnology and Pharmacological Sciences, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, 70125 Bari, Italy. magmon@farmbiol.uniba.it
Magnus
M
Monné
Daniela Valeria
DV
Miniero
Vito
V
Iacobazzi
Faustino
F
Bisaccia
Giuseppe
G
Fiermonte
D019943:Amino Acid Substitution; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002417:Cattle; D003593:Cytoplasm / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli; D006801:Humans; D007656:Ketoglutaric Acids / Q000737:chemistry / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D016296:Mutagenesis; D020125:Mutation, Missense; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
D007656:Ketoglutaric Acids; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; C021723:oxoglutarate translocator