Febs Letters Volume 61, Number 1-2./Volume 62, Number 1-3. [antikvár]

Volume 61, number 1 Fi'.BS LIÍTTF.RS January 1976 Review Letter HORMONE-RECEPTOR INTERACTIONS Ernst J. M. HELMREICH Department of Physiological Chemistry, University of Würzburg, Würzburg, GFR Received 3 November 1975 Hormone-receptor complexes are rather long lived allowing several discrete cycles of activation and deactivation of adenylate cyclase. Regulatory steps are therefore postulated facilitating dissociation of the hormone-receptor complex and modulating coupling between receptor and adenylate cyclase. 1. Hormone receptors and adenylate cyclase At present the translation of hormone—receptor interactions into biological action is not understood. An important, although not universal action which is elicited by the interaction of the hormone with its receptor is the activation of adenylate cyclase. Some hormones, among them epinephrine, glucagon and ACTH, have been shown to act primarily through the product of the adenylate cyclase reaction, the second messenger cyclic 3', 5'-AMP, but some biological effects may not be mediated by cyclic 3', 5'-AMP [1]. In any event, the interaction of hormones with receptors activates in some cases adenylate cyclase but initiates in all cases the biological response. It is therefore necessary to understand the translation of hormone-receptor interactions in order to comprehend the function of hormones. 2. The lifetime of hormone-receptor complexes We have recently summarized the evidence from the literature on the lifetime of hormone-receptor complexes, cf [2]. The 'on' constants {k^) ot the insulin-receptor complex range between 5 X 10' and 1.5 X 10' mol"' sec"' and the 'off constants (.k_ ,) range between 1X10"^ and 3 X lO"'* sec"'. = k^ !k_ , of the insulin-receptor complex and ranges therefore between 5 X 10'® and 5X 10" M"', cf [3|. Thus, the insulin-receptor complex is a tight complex with an accordingly long lifetime. Assuming that dissociation of the hormone-receptor complex |ll| • |R1 - [H] + [R] is first order, t/2 = In 2//t_ , may be calculated; it ranged from 15.6 to 42.8 min at 24°C. Insuhn actions on adenyhite cyclase are doubtful; but similar data have recently been published on neurohypophyseal hormones and membranes from bovine renal medulla. In contrast to insulin important biological actions of these hormones are transmitted via adenylate cyclase activation and 3'. 5'-cAMP. l or vasopressin A, = 3.2 X 10® mol"' sec"' and k_ , = 7.0 X 10"' sec"' and K^^^ = 4.5 X 10' M"' [41. (In a more recent study a A'gj.^ value of 5 X 10' M"' was reported [5]). Thus, tlie iifeume of the vasopressin-receptor complex is lii

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Cím: Febs Letters Volume 61, Number 1-2./Volume 62, Number 1-3. [antikvár]

Szerző: A. M. Kaye , E. Bäuerlein , E. Karlsson , M. J. Eggitt P. V. Postma

Kiadó: North-Holland Publishing Company

Kötés: Könyvkötői kötés

Méret: 200 mm x 270 mm

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