%0 Journal Article %1 Klotz1988 %A Klotz, K. N. %A Lohse, M. J. %A Schwabe, U. %D 1988 %J J Biol Chem %K & Adenosine/analogs Animals Assay Binding, Brain/*metabolism Cell Competitive Compounds/pharmacology Diethyl Ethylmaleimide/pharmacology Kinetics Membrane/metabolism Phenylmercury Purinergic/drug Pyrocarbonate/pharmacology Radioligand Rats Tetranitromethane/pharmacology derivatives/metabolism effects/*metabolism Receptor %N 33 %P 17522-6 %T Chemical modification of A1 adenosine receptors in rat brain membranes. Evidence for histidine in different domains of the ligand binding site %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=3182861 %V 263 %X Chemical modification of amino acid residues was used to probe the ligand recognition site of A1 adenosine receptors from rat brain membranes. The effect of treatment with group-specific reagents on agonist and antagonist radioligand binding was investigated. The histidine-specific reagent diethylpyrocarbonate (DEP) induced a loss of binding of the agonist R-N6-3H phenylisopropyladenosine (3HPIA), which could be prevented in part by agonists, but not by antagonists. DEP treatment induced also a loss of binding of the antagonist 3H8-cyclopentyl-1,3-dipropylxanthine (3HDPCPX). Antagonists protected A1 receptors from this inactivation while agonists did not. This result provided evidence for the existence of at least 2 different histidine residues involved in ligand binding. Consistent with a modification of the binding site, DEP did not alter the affinity of 3HDPCPX, but reduced receptor number. From the selective protection of 3H PIA and 3HDPCPX binding from inactivation, it is concluded that agonists and antagonists occupy different domains at the binding site. Sulfhydryl modifying reagents did not influence antagonist binding, but inhibited agonist binding. This effect is explained by modification of the inhibitory guanine nucleotide binding protein. Pyridoxal 5-phosphate inactivated both 3HPIA and 3HDPCPX binding, but the receptors could not be protected from inactivation by ligands. Therefore, no amino group seems to be located at the ligand binding site. In addition, it was shown that no further amino acids with polar side chains are present. The absence of hydrophilic amino acids from the recognition site of the receptor apart from histidine suggests an explanation for the lack of hydrophilic ligands with high affinity for A1 receptors.

@article{Klotz1988, abstract = {Chemical modification of amino acid residues was used to probe the ligand recognition site of A1 adenosine receptors from rat brain membranes. The effect of treatment with group-specific reagents on agonist and antagonist radioligand binding was investigated. The histidine-specific reagent diethylpyrocarbonate (DEP) induced a loss of binding of the agonist R-N6-[3H] phenylisopropyladenosine ([3H]PIA), which could be prevented in part by agonists, but not by antagonists. DEP treatment induced also a loss of binding of the antagonist [3H]8-cyclopentyl-1,3-dipropylxanthine ([3H]DPCPX). Antagonists protected A1 receptors from this inactivation while agonists did not. This result provided evidence for the existence of at least 2 different histidine residues involved in ligand binding. Consistent with a modification of the binding site, DEP did not alter the affinity of [3H]DPCPX, but reduced receptor number. From the selective protection of [3H] PIA and [3H]DPCPX binding from inactivation, it is concluded that agonists and antagonists occupy different domains at the binding site. Sulfhydryl modifying reagents did not influence antagonist binding, but inhibited agonist binding. This effect is explained by modification of the inhibitory guanine nucleotide binding protein. Pyridoxal 5-phosphate inactivated both [3H]PIA and [3H]DPCPX binding, but the receptors could not be protected from inactivation by ligands. Therefore, no amino group seems to be located at the ligand binding site. In addition, it was shown that no further amino acids with polar side chains are present. The absence of hydrophilic amino acids from the recognition site of the receptor apart from histidine suggests an explanation for the lack of hydrophilic ligands with high affinity for A1 receptors.}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Klotz, K. N. and Lohse, M. J. and Schwabe, U.}, biburl = {https://www.bibsonomy.org/bibtex/21da3ef6d38c28d783445992d77df38cf/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {ac7812fa4d402f32acf23b20ea6e4651}, intrahash = {1da3ef6d38c28d783445992d77df38cf}, issn = {0021-9258 (Print) 0021-9258 (Linking)}, journal = {J Biol Chem}, keywords = {& Adenosine/analogs Animals Assay Binding, Brain/*metabolism Cell Competitive Compounds/pharmacology Diethyl Ethylmaleimide/pharmacology Kinetics Membrane/metabolism Phenylmercury Purinergic/drug Pyrocarbonate/pharmacology Radioligand Rats Tetranitromethane/pharmacology derivatives/metabolism effects/*metabolism Receptor}, month = {Nov 25}, note = {Klotz, K N Lohse, M J Schwabe, U Research Support, Non-U.S. Gov't United states The Journal of biological chemistry J Biol Chem. 1988 Nov 25;263(33):17522-6.}, number = 33, pages = {17522-6}, shorttitle = {Chemical modification of A1 adenosine receptors in rat brain membranes. Evidence for histidine in different domains of the ligand binding site}, timestamp = {2010-12-14T18:20:05.000+0100}, title = {Chemical modification of A1 adenosine receptors in rat brain membranes. Evidence for histidine in different domains of the ligand binding site}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=3182861}, volume = 263, year = 1988 }