A(2A) adenosine receptors were examined in bovine striatal membranes following exposure to tetranitromethane (TNM) which modifies tyrosine and cysteine residues. TNM (0.05-0.5 mM) treatment caused an irreversible, concentration-dependent decrease in the binding activity of the selective A(2A) agonist [H-3]CGS 21680. Protection studies showed that TNM inactivation could be prevented by the adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) and by the antagonist xanthine amine congener (XAC), suggesting that TNM modified residues at the ligand-binding sites. Scatchard analysis of the binding data showed that 0.15 mM TNM decreased the [H-3]CGS 21680 B-max value from 447 +/- 39 to 273 +/- 21 fmol/mg of proteins without any significant change in the K-d values (13.5 +/- 1.4 and 14.7 +/- 1.5 for control and treated membranes, respectively). We carried out a series of successive chemical modifications with the reducing agent dithiothreitol (DTT), which indicated that the residues modified by TNM, under our experimental conditions, are tyrosine residues and not cysteine residues.
|Autori:||MARTINI C; TRINCAVELLI L; LUCACCHINI A|
|Titolo:||Chemical modifications of striatal A(2A) adenosine receptors: A possible role for tyrosine at the ligand binding sites|
|Anno del prodotto:||1997|
|Digital Object Identifier (DOI):||10.1016/S0005-2736(96)00243-X|
|Appare nelle tipologie:||1.1 Articolo in rivista|