THE MECHANISM OF PROLINE GLUTAMATE ANTIPORT IN RAT-KIDNEY MITOCHONDRIA - ENERGY-DEPENDENCE AND GLUTAMATE-CARRIER INVOLVEMENT/

Proline/glutamate antiport in rat kidney mitochondria has been studied in terms of two different features: energy dependence and glutamate-c arrier contribution to accomplish proline movement across the mitochon drial membrane. Energy dependence of the proline/glutamate antiporter in rat kidney mitochondria has been investigated by means of both spec troscopic measurements and isotopic techniques, using either normal or [C-14]glutamate-loaded mitochondria. The sensitivity of the proline/g lutamate antiport to the ionophores valinomycin and nigericin, under c onditions in which Delta Psi and Delta pH are selectively affected, sh ows that the exchange is energy dependent. Measurements of both membra ne potential and proton movement across the mitochondrial membrane sug gest that proline/glutamate antiport is driven by the electrochemical proton gradient via the Delta Psi dependent proline/glutamate transloc ator and Delta pH-dependent glutamate/ OH- carrier. Such a carrier pro vides for re-uptake of glutamate that has already passed out of the mi tochondria in exchange with incoming proline, made possible by the exi stence of a separate pool of glutamate in the intermembrane space, dir ectly shown by means of HPLC measurements.