A soluble angiotensin II-binding protein from rabbit liver.

An angiotensin II-binding activity has been detected in the 100,000 x g supernatant fraction of rabbit liver. The total amount of binding activity in this fraction was substantially greater than that which could be solubilized from hepatic particles by treatment with digitonin. The crude soluble binding activity resembled the binding protein which had been purified from the particles in several respects. First, binding required the presence of p-chloromercuriphenylsulfonic acid and bound angiotensin II was released by dithiothreitol. Second, the molecular weight of the responsible protein cross-linked to radioiodinated angiotensin II was about 75,000 in the reduced, denatured state. Finally, guinea pig antiserum raised against the binding protein that had been purified from particles reacted identically with the soluble and solubilized activities.