Target recognition of guanylate cyclase by guanylate cyclase-activating proteins.
Guanylate cyclase-activating proteins (GCAPs) control the activity of membrane bound guanylate cyclases in vertebrate photoreceptor cells. They form a permanent complex with guanylate cyclase 1 (ROS-GC1) at low and high Ca2+-concentrations. Five different target regions of GCAP-1 have been identified in ROS-GC1 at rather distant sites. These findings could indicate a multipoint attachment site for GCAP-1 or, alternatively, the presence of transient binding sites with short contact to GCAP-1. In addition some data are consistent with the operation of one or more transducer units, that represent regulatory regions without being direct binding sites. A permanent ROS-GC1/GCAP-1 complex is physiologically significant, since it allows a very short response time of cyclase activity when the intracellular Ca2+-concentration changes. Thereby, activation of cyclase participates in speeding up the recovery of the photoresponse after illumination and restores the circulating dark current.
Koch
Karl-Wilhelm
KW
Institut für Biologische Informationsverarbeitung 1, Forschungszentrum Jülich, D-52425 Jülich, Germany. k.w.koch@fz-juelich.de
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019281:Dimerization; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins; D008027:Light; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012374:Rod Cell Outer Segment / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D003432:Cross-Linking Reagents; D051604:Guanylate Cyclase-Activating Proteins; D006162:Guanylate Cyclase; D002118:Calcium