The dicyclohexylcarbodiimide‐binding protein of the mitochondrial ATPase complex from beef heart

N,N’-Dicyclohexylcarbodiimide (DCCD) was intro- duced as an inhibitor of oxidative phosphorylation in beef heart mitochondria [ 11. This hydrophobic car- bodiimide specifically acts, like the antibiotic oli- gomycin, on the membrane-integrated part of the mitochondrial ATPase complex [2,3]. The irreversible mode of action allowed the identification of a DCCD- binding protein on the level of whole mitochondria [4] as well as of the purified oligomycin-sensitive ATPase [5]. This protein has been referred to as pro- teolipid due to its solubility in neutral chloroform/ methanol [4]. The isolation of the DCCD-binding protein has been attempted [4], but it is uncertain whether it has been obtained in pure form, since it was never characterized in more detail. In the meantime, DCCD-binding proteins have been identified in mitochondria from different sources [6-81, in chloroplasts [9] and in bacterial plasma membranes [ 10,111. Some of them could be purified by a specific extraction with chloroform/methanol or with butanol. The bacterial protein was obtained in homogeneous form after DEAE-chromatography in the presence of chloroform/methanol [lo]. The present communication describes the purifica- tion of the DCCD-binding protein from beef heart mitochondria. The procedure involves a gentle extrac- tion with chloroform/methanol [lo] followed by + Present Address: Gesellschaft ftir Biotechnologische Forschung, Mascheroder Weg 1, D-3300 Braunschweig-Stijckheim, FRG