Phosphate transport in rat liver mitochondria: Location of sulfhydryl groups essential for transport activities

The membrane orientation and symmetry of protein thiol group(s) necessary for transport of P_i in rat liver mitochondria have been assessed by comparing inhibition of transport in intact mitochondria to that in inverted vesicles of purified inner membrane. The permeability characteristics of a variety of inhibitors have been determined under specified conditions. The sensitivities of the uptake pathways in mitochondria and in inverted vesicles appear thus far to be identical. By comparing results with permeant and nonpermeant inhibitors, or sequential treatment with different inhibitors, arguments can be made in favor of a single reorienting site of thiol sensitivity.