Photoaffinity labeling of A\(_1\) adenosine receptors
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- The ligand-binding subunit of the A\(_1\)-adenosine receptor has been identified by photoaffinity labeling. A photolabile derivative of R- \(N^6\)-phenylisopropyladenosine, R-2-azido-\(N^6\)-p-hydroxyphenylisopropyladenosine (R-AHPIA), has been synthesized as a covalent specific Iigand for A\(_1\)-adenosine receptors. In adenylate cyclase studies with membranes of rat fat cells and human platelets, R·AHPIA has adenosine receptor agonist activity with a more than 60-fold selectivity for the A\(_1\)-subtype. It competes for [\(^3\)H].\(N^6\)-The ligand-binding subunit of the A\(_1\)-adenosine receptor has been identified by photoaffinity labeling. A photolabile derivative of R- \(N^6\)-phenylisopropyladenosine, R-2-azido-\(N^6\)-p-hydroxyphenylisopropyladenosine (R-AHPIA), has been synthesized as a covalent specific Iigand for A\(_1\)-adenosine receptors. In adenylate cyclase studies with membranes of rat fat cells and human platelets, R·AHPIA has adenosine receptor agonist activity with a more than 60-fold selectivity for the A\(_1\)-subtype. It competes for [\(^3\)H].\(N^6\)- phenylisopropyladenosine binding to Arreceptors of rat brain membranes with a Ki value of 1.6 nM. After UV irradiation, R-AHPIA binds irreversibly to the receptor, as indicated by a loss of [\(^3\)H)\(N^6\)-phenylisopropyladenosine binding afterextensive washing; the K; value for this photoinactivation is 1.3 nM. The p-hydroxyphenyl substituent of R-AHPIA can be directly radioiodinated to give a photoaffinity Iabel of high specific radioactivity (\(^{125}\)I-AHPIA). This compound has a KD value of about 1.5 nM as assessed from saturation and kinetic experiments. Adenosine analogues compete for \(^{125}\)I-AHPIA binding to rat brain membranes with an order of potency characteristic for A\(_1\)-adenosine receptors. Dissociation curves following UV irradiation at equilibrium demonstrate 30-40% irreversible specific binding. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that the probe is photoincorporated into a single peptide of M\(_r\) = 35,000. Labeling of this peptide can be blocked specifically and stereoselectively by adenosine receptor agonists and antagonists in a manner which is typical for the A\(_1\)-subtype. The results indicate that \(^{125}\)I-AHPIA identifies the ligand-binding subunit of the A\(_1\)-adenosine receptor, which is a peptide with M\(_r\) = 35,000.…
Autor(en): | Karl-Norbert Klotz, G. Cristalli, M. Grifantini, S. Vittori, M. J. Lohse |
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URN: | urn:nbn:de:bvb:20-opus-60198 |
Dokumentart: | Artikel / Aufsatz in einer Zeitschrift |
Institute der Universität: | Medizinische Fakultät / Institut für Pharmakologie und Toxikologie |
Sprache der Veröffentlichung: | Englisch |
Titel des übergeordneten Werkes / der Zeitschrift (Deutsch): | The journal of biological chemistry |
Erscheinungsjahr: | 1985 |
Band / Jahrgang: | 27 |
Heft / Ausgabe: | 260 |
Originalveröffentlichung / Quelle: | The journal of biological chemistry (1985) 27, 260, 14659-14664. |
Allgemeine fachliche Zuordnung (DDC-Klassifikation): | 6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit |
Normierte Schlagworte (GND): | Toxikologie |
Datum der Freischaltung: | 06.12.2011 |
Lizenz (Deutsch): | Deutsches Urheberrecht |