IDENTIFICATION OF THE N-ETHYLMALEIMIDE REACTIVE PROTEIN OF THE MITOCHONDRIAL PHOSPHATE TRANSPORTER

The mitochondrial phosphate carrier is inhibited by the SH reagents p-(hydroxymercuri)benzoate and N-ethylmaleimide. Based on an analysis utilizing dodecyl sulfate-polyacrylamide gels, an SH-containing 32000-dalton protein has been identified as a component of the phosphate carrier system. Two other N-[3H]ethylmaleimide-labeled proteins of the inner mitochondrial membrane have been eliminated from this role [Wohlrab, H., & Greaney, J., Jr. (1978) Biochim. Biophys. Acta 503, 425] on the basis that band IV (45 000 daltons) is absent from heart sonic submi-tochondrial particles and band VII (6 500 daltons) does not react with p-(hydroxymercuri)benzoate. The mobility of the 32000-dalton protein (0.43) is lower than that of the γ subunit of the mitochondrial ATPase (0.46) and the carboxyatrac-tyloside binding protein (0.48) on 12.5% dodecyl sulfate-polyacrylamide gels. In these flight muscle mitochondria, 0.87 nmol of N-[3H]ethylmaleimide per nmol of cytochrome a is bound to the 32,000-dalton protein. © 1979, American Chemical Society. All rights reserved.