Calcium Modulation of Bovine Photoreceptor Guanylate Cyclase

• Published in: Biochemistry (Easton) 1996-07, Vol.35 (26), p.8478-8482
• Main Authors: Duda, Teresa, Goraczniak, Rafal, Surgucheva, Irina, Rudnicka-Nawrot, Maria, Gorczyca, Wojciech A, Palczewski, Krzysztof, Sitaramayya, Ari, Baehr, Wolfgang, Sharma, Rameshwar K
• Format: Article
• Language: English
• Subjects: Animals; Calcium - metabolism; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cattle; Cell Line, Transformed; Cercopithecus aethiops; Guanylate Cyclase - genetics; Guanylate Cyclase - metabolism; Guanylate Cyclase-Activating Proteins; Mutagenesis, Site-Directed; Photoreceptor Cells - enzymology; Recombinant Proteins - genetics; Recombinant Proteins - metabolism
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi960752z

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 Ca2+-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 μM). 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.