THE IMMOBILIZED MATRIX BUFFER CONTROLS THE RATE OF MITOCHONDRIAL RESPIRATION IN STATE 3(P) ACCORDING TO CHANCE

Preparations of coupled mitochondria were labeled with fluorescein iso thiocyanate (FITC). Comparison of characteristics of FITC bound to mit ochondria versus azolectin liposomes indicates that a significant part of the probe is bound to mitochondrial proteins including proteins of the matrix side of the inner membrane. The experiments with the probe indicate that mitochondrial proteins resemble typical polyelectrolyte s with constant of dissociation close to 10(-7). H+ and K+ compete for binding to mitochondrial proteins at neutral pH. The slow deprotonati on of matrix proteins is observed during equilibration of matrix proto ns with medium protons. This process is not restricted to the transmem brane proton transfer. The data are explained by the theory of the imm obilized buffer. Under certain conditions the extent of dissociation o f the matrix immobilized buffer correlates with the rate of mitochondr ial respiration in state 3(P) according to Chance.