RESPIRATION IN NON-PHOSPHORYLATING YEAST MITOCHONDRIA - ROLES OF NONOHMIC PROTON CONDUCTANCE AND INTRINSIC UNCOUPLING

Respiratory rate, protonmotive force and charge/O ratio were measured under two different kinds of steady state ill non-phosphorylating yeast mitochondria: (i) when the electron flux was modulated by a variable limitation in electron supply or (ii) when oxygen consumption was decreased by respiratory chain inhibitor titration. We showed that the relationships between either DELTA-p or charge/O ratio and respiratory rate are different under the two kinds of steady state, indicating different degrees of intrinsic uncoupling in respiratory chain. Moreover, we observed a non-ohmic dependence between H+-conductance and DELTA-p. We concluded that the high rate of static-head respiration in yeast mitochondria was determined both by the non-ohmic proton conductance of the inner membrane and the saturation of the redox proton pump slipping.