The reactivity of -SH groups in the ADP/ATP carrier isolated from beef heart mitochondria.
The emergence of the reactivity of -SH groups associated with conformation changes has been studied on the ADP/ATP carrier, is isolated in three different inhibitor-protein complexes. 1. The bongkrekate-protein complex incorporates approximately one molecular more of N-ethylmaleimide than the carboxyatractylate-protein complex. After extensive denaturation by dodecylsulfate in urea, both inhibitor complexes exhibit four reactive -SH groups per subunit. Thus one of four -SH groups per subunit has been unmasked in the bongkrekate-protein complex. 2. The interconversion from the bongkrekate-protein complex to the carboxyatractylate-protein complex is inhibited after the -SH groups have been blocked. 3. The protein complex isolated with the more easily dissociable atractylate, is used to demonstrate, by the emergence of the -SH groups, the transition into the m-state. This transition is specifically catalyzed by ADP and ATP. 4. Using 2,2'-dinitro-5,5'-dithiodibenzoate, the appearance of the -SH groups on transition from the c-state to the m-state can be followed spectrophotometrically. The specificity for the catalyzing nucleotides is identical with that for the transport. The Km for ADP and ATP is in the range of 1 microM. In conclusion, the thiol groups of the isolated ADP/ATP carrier behave as in the mitochondrial membrane. The unmasking of -SH groups is in full accordance with the concept of two conformational states (c and m).
D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D001865:Bongkrekic Acid / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D066298:In Vitro Techniques; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013997:Time Factors
D002352:Carrier Proteins; D013438:Sulfhydryl Compounds; C023428:carboxyatractylate-binding protein, rat; D001865:Bongkrekic Acid; D000244:Adenosine Diphosphate; D000226:Mitochondrial ADP, ATP Translocases; D009713:Nucleotidyltransferases