title: Photoaffinity cross-linked A1 adenosine receptor-binding subunits. Homologous glycoprotein expression by different tissues.
abstract: Mammalian A1 adenosine receptor-binding peptides can be visualized by covalently labeling them with the photoaffinity cross-linking ligand N6-2-(4-amino-3-[125I] iodophenyl)ethyladenosine followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis/autoradiography. The proteins comprising the A1 adenosine receptor-binding subunit of rat brain and fat migrate with Mr 38,000. In this study, the glycoproteins representing the radiolabeled A1 adenosine receptor-binding subunit expressed in each of these tissues (brain and fat) were compared through the use of peptide mapping and exo- and endoglycosidase treatments. Peptide mapping studies with several enzymes demonstrate that the protein component of the radiolabeled A1 adenosine receptor-binding subunit is conserved between different tissues. Both labeled receptor peptides demonstrate a sensitivity to neuraminidase as evidenced by increased mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggesting that the receptors contain complex-type carbohydrate chains. Insensitivity to alpha-mannosidase suggests a lack of high mannose-type carbohydrate chains. Deglycosylation of the labeled receptor-binding subunits with endoglycosidase F results in a single labeled polypeptide of Mr 32,000 for both systems. These data suggest that the A1 adenosine receptor-binding subunits expressed in the rat brain and fat are similar glycoproteins as evidenced by similar overall molecular weights, identical peptide maps, and equivalent responses to endo- and exoglycosidase treatment.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D000273:Adipose Tissue / Q000378:metabolism*; D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009928:Organ Specificity; D051381:Rats; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D011983:Receptors, Purinergic
chemical_list: D000345:Affinity Labels; D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; C046507:N(6)-2-(4-amino-3-iodophenyl)ethyladenosine; D000241:Adenosine