title: Light- and nucleotide-dependent binding of phosphodiesterase to rod disk membranes: correlation with light-scattering changes and vesicle aggregation.
abstract: Under conditions in which large guanosine cyclic 3',5'-phosphate (cGMP)- and phosphodiesterase (PDE)-dependent changes in near-infrared transmission and vesicle aggregation and disaggregation occur, we have observed a striking change in the binding of PDE to rod disk membranes. The change in PDE binding is nucleotide and light dependent as are the light-scattering changes. The cGMP- and PDE-dependent light-scattering signal can be produced by a 500-nm light flash which bleaches 1/(1 X 10(7] rhodopsin molecules. Mg ions are an essential cofactor for the nucleotide-dependent PDE binding and light-scattering changes. 3-Isobutyl-1-methylxanthine and other competitive inhibitors of PDE hydrolytic activity support increased PDE binding to the disk membrane, vesicle aggregation, and the light-scattering signal. However, treatments which block GTP-dependent activation of PDE hydrolytic activity (colchicine, GDP, or ethylenediaminetetraacetic acid) also block these phenomena. Thus, GTP-dependent activation of PDE rather than its hydrolytic activity appears to be correlated with the light-scattering signal.
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007700:Kinetics; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D010786:Photoreceptor Cells / Q000378:metabolism*; D012168:Retinal Pigments / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D012542:Scattering, Radiation
chemical_list: D012168:Retinal Pigments; D015636:Magnesium Chloride; D006160:Guanosine Triphosphate; D012243:Rhodopsin; D004492:Edetic Acid; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006152:Cyclic GMP; D008274:Magnesium; D002122:Calcium Chloride; D003078:Colchicine