Adenosine Receptor Permanently Coupled to Turkey Erythrocyte Adenylate Cyclase

Sergei Braun, Alexander Levitzki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

The mode of coupling of the adenosine receptor to adenylate cyclase in turkey erythrocyte membranes was probed by two independent approaches. The progressive inactivation of the adenosine receptor by an adenosine receptor affinity label resulted in the proportional reduction in the adenosine plus GppNHp dependent specific activity. In contrast, the intrinsic rate constant (k3), characterizing the process of adenylate cyclase activation by the adenosine-adenosine receptor complex, is independent of the extent of receptor inactivation. This behavior favors the precoupled A+R E.Ka ⇌mechanism, A + R.E⇌ka A.R.E⇌k3 k4 ARE', where the receptor R and the enzyme E are permanently coupled to each other and the adenosine A binds to the receptor and induces the first-order process of cyclase activation to its active form ARE'. The finding that adenosine receptor is permanently coupled to the cyclase catalytic unit is corroborated by the observation that the progressive increase in membrane fluidity has no effect on the rate constant (k3) of adenylate cyclase activation by the adenosine-adenosine receptor complex and that the dose-response curve for adenosine is noncooperative.

Original languageEnglish
Pages (from-to)2134-2138
Number of pages5
JournalBiochemistry
Volume18
Issue number10
DOIs
StatePublished - 1979

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