Proton-translocating adenosinetriphosphatase in rough and smooth microsomes from rat liver.

Rat liver smooth and rough microsomal membranes exhibit an ATP-dependent H+ transport which can be inhibited by sulfhydryl reagents and dicyclohexylcarbodiimide but is resistant to oligomycin. On the basis of inhibitor sensitivities and substrate specificities, this H+ pump was found to be different from that of mitochondria, lysosomes, gastric H+-K+-ATPase, and yeast plasma membrane H+-ATPase but to resemble that of endocytic vesicles and the H+ pump responsible for urinary acidification. The transport process is accelerated by valinomycin in the presence of potassium, suggesting that it is an electrogenic pump. The same fractions were enriched in an ATPase with inhibitor sensitivities similar to those of the transport activity. It is possible that the proton electrochemical gradients generated by this pump may play a role in the translocation of proteins and sugars, two of the major functions of these structures.