REGULATION OF THE H+ E(-) STOICHIOMETRY OF CYTOCHROME-C-OXIDASE FROM BOVINE HEART BY INTRAMITOCHONDRIAL ATP/ADP RATIOS/

This paper describes the effect of intramitochondrial ATP/ADP ratios o n the H+/e(-) stoichiometry of reconstituted cytochrome c oxidase (COX ) from bovine heart, At 100% intraliposomal ATP the H+/e(-) stoichiome try of the reconstituted enzyme is decreased to half of the value meas ured below 98% intraliposomal ATP (above 2% ADP), while it remains con stant up to 100% ADP. The decrease is obtained with different COX prep arations, independent of the absolute value of the H+/e(-) stoichiomet ry. Decrease of H+/e(-) stoichiometry is prevented by preincubation of the enzyme with a tissue-specific monoclonal antibody to subunit VIa- H (Heart-type). Tissue-specific regulation of the efficiency of energy transduction in COX of muscle mitochondria could have a physiological function in maintaining the body temperature at rest or sleep, i.e. a t low ATP expenditure.