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Interactions of adrenocorticotropic hormone with its adrenal receptors. Degradation of ACTH-1-24 and ACTH-11-24.

1975; Elsevier BV; Volume: 250; Issue: 5 Linguagem: Inglês

10.1016/s0021-9258(19)41747-x

1083-351X

J.M. Saez, A Dazord, A.M. Morera, Pierre Bataille,

Cancer, Hypoxia, and Metabolism

Crude membranes (20,000 x g pellet) prepared from human, rat, and ovine adrenals bind 1251-corticotropin-(l-24)tetracosapeptide (rz51-ACTH1-& and degrade unbound hormone.The degradation is dependent on temperature and the concentration of membrane proteins.The degradation of 1251-[9-tryptophan(o-nitrophenylsulfenyl)] -corticotropin -(1 -24) -tetracosapeptide (rz51 -NPS -ACTHI-21) is similar to 1251-ACTH1-24, but that of 1251-corticotropin-(11-24)-tetradecapeptide (1251-ACTH11-24) is larger.The degradation of 1251-ACTH1-24 is inhibited by ACTH1-24 and corticotropin-( 1 -IO)-decapeptide (ACTH&, but ACTHll-z4 at the same molar concentration has no effect.On the other hand, the degradation of 1251-ACTH11W2, is protected by ACTHll-24 and ACTHI-24, but not by ACTHlmlO.This suggests two systems of degradation, one will have the NH2-terminal sequence of ACTH,-2, as substrate, and the other the 11-24 COOH-terminal sequence.The main labeled product from the degradation of the 1251-ACTH1-24 and 1251-ACTH11-2, behaves as [1251]monoiodotyrosine on Sephadex G-50 and paper chromatography.The independence of ACTH binding to its receptor and degradation is demonstrated by the following facts.(a) Calcium and pancreatic trypsin inhibitor completely inhibit the binding at concentrations when the degradation is not altered; (b) the sequences of peptides of ACTH which inhibit the binding and degradation of 1251-ACTH,.24 are different.