Abstract
A1 adenosine receptors from rat brain membranes were solubilized with
the zwitterionic detergent 3-3-(cholamidopropyl)dimethylammonio-1-propanesulfonate.
The solubilized receptors retained all the characteristics of membrane-bound
A1 adenosine receptors. A high and a low agonist affinity state for
the radiolabelled agonist (R)-N6-3Hphenylisopropyladenosine(3HPIA)
with KD values of 0.3 and 12 nM, respectively, were detected. High-affinity
agonist binding was regulated by guanine nucleotides. In addition
agonist binding was still modulated by divalent cations. The solubilized
A1 adenosine receptors could be labelled not only with the agonist
3HPIA but also with the antagonist 1,3-diethyl-8-3Hphenylxanthine.
Guanine nucleotides did not affect antagonist binding as reported
for membrane-bound receptors. These results suggest that the solubilized
receptors are still coupled to the guanine nucleotide binding protein
Ni and that all regulatory functions are retained on solubilization.
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