title: Expression level and activity profile of membrane bound guanylate cyclase type 2 in rod outer segments.
abstract: Rod and cone cells of the mammalian retina harbor two types of a membrane bound guanylate cyclase (GC), rod outer segment guanylate cyclase type 1 (ROS-GC1) and ROS-GC2. Both enzymes are regulated by small Ca(2+)-binding proteins named GC-activating proteins that operate as Ca2+ sensors and enable cyclases to respond to changes of intracellular Ca2+after illumination. We determined the expression level of ROS-GC2 in bovine ROS preparations and compared it with the level of ROS-GC1 in ROSs. The molar ratio of a ROS-GC2 dimer to rhodopsin was 1 : 13 200. The amount of ROS-GC1 was 25-fold higher than the amount of ROS-GC2. Heterologously expressed ROS-GC2 was differentially activated by GC-activating protein 1 and 2 at low free Ca2+ concentrations. Mutants of GC-activating protein 2 modulated ROS-GC2 in a manner different from their action on ROS-GC1 indicating that the Ca2+ sensitivity of the Ca2+ sensor is controlled by the mode of target-sensor interaction.
authors.affiliation: Biochemistry group, Institute of Biology and Environmental Sciences, Faculty V, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Helten
authors.forename: Werner
authors.initials: W
authors.lastname: Säftel
authors.forename: Karl-Wilhelm
authors.initials: KW
authors.lastname: Koch
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology*; D006152:Cyclic GMP / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006162:Guanylate Cyclase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D011956:Receptors, Cell Surface / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D017948:Retinal Rod Photoreceptor Cells / Q000201:enzymology*; D014785:Vision, Ocular / Q000502:physiology*
chemical_list: D051604:Guanylate Cyclase-Activating Proteins; D011956:Receptors, Cell Surface; C110715:guanylate cyclase 1; C484784:GUCY2F protein, human; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D002118:Calcium