IDENTIFICATION OF AN ATP-DEPENDENT COPPER TRANSPORT-SYSTEM IN ENDOPLASMIC-RETICULUM VESICLES ISOLATED FROM RAT-LIVER

1. This paper identifies and characterizes an ATP-dependent copper tra nsport system in endoplasmic reticulum vesicles isolated from male rat liver. 2. The transporter has a K-m of 2.5 +/- 1.2 mu mol l(-1) coppe r glutathione (CuGSH) and a V-max of 4.5 +/- 1.3 nmol (mg protein)(-1) (5 min)(-1) for copper.3. At a copper concentration of 2 mu mol l(-1) , ATP dependence reaches saturation, with a K, for ATP of 4.7 +/- 2.4 mmol l(-1) and a V-max of 2.8 +/- 0.8 nmol (mg protein)(-1) (5 min)(-1 ). 4. The uptake is dependent on ATP hydrolysis, since a low energy an alogue of ATP, adenosine 5'-[beta-gamma-methylene] triphosphate tetral ithium (AMP.PCP), has no effect on copper uptake. 5. The transporter i s a P-type ATPase, since vanadate inhibits uptake with a high degree o f specificity (100 mu mol l(-1) inhibits uptake by 50% at a copper con centration of 2 mu mol l(-1)).