title: Calcium modulation of bovine photoreceptor guanylate cyclase.
abstract: Bovine photoreceptor guanylate cyclase (ROS-GC) consists of a single transmembrane polypeptide chain with extracellular and intracellular domains. In contrast to non-photoreceptor guanylate cyclases (GCs) which are activated by hormone peptides, ROS-GC is modulated in low Ca2+ by calmodulin-like Ca(2+)-binding proteins termed GCAPs (guanylate cyclase-activating proteins). In this communication we show that, like the native system, ROS-GC expressed in COS cells is activated 4-6-fold by recombinant GCAP1 at 10 nM Ca2+ and that the reconstituted system is inhibited at physiological levels of Ca2+ (1 microM). A mutant ROS-GC in which the extracellular domain was deleted was stimulated by GCAP1 indistinguishable from native ROS-GC indicating that this domain is not involved in Ca2+ modulation. Deletion of the intracellular kinase-like domain diminished the stimulation by GCAP1, indicating that this domain is at least in part involved in Ca2+ modulation. Replacement of the catalytic domain in a non-photoreceptor GC by the catalytic domain of ROS-GC yielded a chimeric GC that was sensitive to ANF/ATP and to a lesser extent to GCAP1. The results establish that GCAP1 acts at an intracellular domain, suggesting a mechanism of photoreceptor GC stimulation fundamentally distinct from hormone peptide stimulation of other cyclase receptors.
authors.affiliation: Department of Cell Biology, University of Medicine and Dentistry of New Jersey, Stratford 08084, USA.
authors.forename: T
authors.initials: T
authors.lastname: Duda
authors.forename: R
authors.initials: R
authors.lastname: Goraczniak
authors.forename: I
authors.initials: I
authors.lastname: Surgucheva
authors.forename: M
authors.initials: M
authors.lastname: Rudnicka-Nawrot
authors.forename: W A
authors.initials: WA
authors.lastname: Gorczyca
authors.forename: K
authors.initials: K
authors.lastname: Palczewski
authors.forename: A
authors.initials: A
authors.lastname: Sitaramayya
authors.forename: W
authors.initials: W
authors.lastname: Baehr
authors.forename: R K
authors.initials: RK
authors.lastname: Sharma
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins; D016297:Mutagenesis, Site-Directed; D010786:Photoreceptor Cells / Q000201:enzymology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D051604:Guanylate Cyclase-Activating Proteins; D011994:Recombinant Proteins; D006162:Guanylate Cyclase; D002118:Calcium