Abstract
The glutamine carrier from rat kidney mitochondria, solubilized in dodecyl octaoxyethylene ether (C12E8) and partly purified on hydroxyapatite, was identified and completely purified by Celite chromatography. On SDS/PAGE, the purified glutamine carrier consisted of a single protein band with an apparent molecular mass of 41.5 kDa. When reconstituted into liposomes, the glutamine carrier catalysed both the unidirectional flux of glutamine and the glutamine/glutamine countertransport, which were completely inhibitable by a mixture of pyridoxal 5'-phosphate and N-ethylmaleimide. The carrier protein was purified 474-fold with a recovery of 58% and a protein yield of 0.12% with respect to the mitochondrial extract. The glutamine carrier-mediated transport is quite specific for l-glutamine. l-Asparagine is the only other amino acid that is efficiently transported by the reconstituted carrier protein. d-Glutamine, l-glutamate and l-aspartate are very poor substrates. The transport activity was inhibited by several thiol-group and amino-group reagents.