Coupling of the alpha 1-adrenergic receptor to a guanine nucleotide-binding regulatory protein by a discrete domain distinct from its ligand recognition site.
Coupling of the alpha 1-adrenergic receptor to a guanine nucleotide-binding regulatory protein by a discrete domain distinct from its ligand recognition site.
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α1-肾上腺素能受体通过与其配体识别位点不同的离散结构域与鸟嘌呤核苷酸结合调节蛋白偶联。
DOI：
10.1016/0167-4889(88)90051-1
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Homcy,CJ
中科院分区：
文献类型：
--
作者：
Graham,RM;Sena,LM;Longabaugh,JP;Sawutz,DG;Schwarz,KR;Homcy,CJ
At rat hepatic membraneα1-adrenergic receptors, the nonhydrolyzable GTP analogue p[NH]ppG causes a rightward shift of agonist competition curves and a loss of high-affinity binding. This p[NH]ppG effect is consistent with the involvement of a guanine nucleotide-binding regulatory protein (G-protein) inα1-adrenergic receptor signalling. Although readily apparent in membranes prepared to avoid retention of endogenous nucleotides and activation of Ca2+-sensitive proteinases (+pi), this p[NH]ppG effect is not observed in membranes prepared without proteinase inhibitors (−pi), or in −pi membranes treated with Ca2+(−pi, +Ca2+). In these various membrane preparations, differentMrforms of the receptor are also identified by photoaffinity labelling with [125I]CP65 526, an aryl azide analog of theα1-selective antagonist, prazosin, followed by SDS-polyacrylamide gel electrophoresis and autoradiography. Whereas a predominantMr= 80 000 subunit is identified in +pi membranes, in −pi membranes a proteolyticMr= 59 000 fragment is also observed. In −pi, +Ca2+membranes, only this latter peptide is detected. To evaluate the ability of each of these forms of the receptor to couple with a G-protein, the effect of p[NH]ppG on the agonist-inhibition of [125I]CP65 526 labelling was determined by laser densitometry scanning and computer analysis. At theMr= 80 000 subunit, p[NH]ppG causes a rightward shift of agonist competition curves and a loss of high-affinity binding, even in −pi membranes. By contrast, agonist-binding at theMr= 59 000 subunit is of low-affinity and was not affected by p[NH]ppG. These data indicate that the cleavedMr= 59 000 fragment, while retaining hormone binding activity is unable to undergo G-protein coupling. Thus, theα1-adrenergic receptor appears to contain a discrete domain necessary for G-protein coupling that is distinct from its ligand recognition site.
