2-Mercaptopropionylglycine restores activity of oligomycin-sensitive ATPase to control values following treatment with carbonylcyanide-p-trifluoromethoxyphenylhydrazone.

We have shown [l] that the intensity of band 4 (mol. wt 3 1 000, nomenclature from [2]) of oligomycin-sensitive ATPase from beef heart mitochondria increases in the presence of thiol reagent, 2-mercaptopropionylglycine. Here we show that the intensity of this band (which is lacking in oligomycin-insensitive ATPase [3]) decreases in the presence of 0.2 MM of the uncoupler carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP). This decrease in band intensity is restored to the control level by subsequent treatment with 14 nmol/mg protein of 2-mercaptopropionylglycine. Furthermore, ATPase activity increased by FCCP is restored to the control level by 2-mercaptopropionylglycine. Spin labeling of the mitochondrial ATPase with short and long chain maleimide labels was carried out. Sequential treatment with FCCP and 2-mercaptopropionylglycine revealed that mobile sulfhydryl regions of the ATPase molecule are stabilized by the thiol reagent against reduction induced by FCCP.