| Abstract: | The characteristics of the basic amino acid permease (system VI) of the filamentous fungus Penicillium chrysogenum were studied in plasma membranes fused with liposomes containing the beef heart mitochondrial cytochrome c oxidase. In the presence of reduced cytochrome c, the hybrid membranes accumulated the basic amino acids arginine and lysine. Inhibition studies with analogs revealed a narrow substrate specificity. Within the external pH range of 5.5 to 7.5, the transmembrane electrical potential (delta psi) functions as the main driving force for uphill transport of arginine, although a low level of uptake was observed when only a transmembrane pH gradient was present. It is concluded that the basic amino acid permease is a H+ symporter. Quantitative analysis of the steady-state levels of arginine uptake in relation to the proton motive force suggests a H+-arginine symport stoichiometry of one to one. Efflux studies demonstrated that the basic amino acid permease functions in a reversible manner. |
