The effect of recoverin-like calcium-binding proteins on the photoresponse of retinal rods.
The rod photoresponse is triggered by an enzyme cascade that stimulates cGMP hydrolysis. The resulting fall in cGMP leads to a decrease in Ca2+, which promotes photoresponse recovery by activating guanylate cyclase, causing cGMP resynthesis. In vitro biochemical studies suggest that Ca2+ activation of guanylate cyclase is medicated by recoverin, a 26 kd Ca(2+)-binding protein. To evaluate this, exogenous bovine recoverin and two other homologous Ca(2+)-binding proteins from chicken and Gecko retina were dialyzed into functionally intact Gecko rods using whole-cell recording. All three proteins prolonged the rising phase of the photoresponse without affecting the kinetics of response recovery. These results suggest that recoverin-like proteins affect termination of the transduction cascade, rather than mediate Ca(2+)-sensitive activation of guanylate cyclase.
Gray-Keller
M P
MP
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
Polans
A S
AS
Palczewski
K
K
Detwiler
P B
PB
D000818:Animals; D000951:Antigens, Neoplasm / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D004594:Electrophysiology; D005136:Eye Proteins; D051597:Hippocalcin; D008027:Light; D008074:Lipoproteins; D008116:Lizards; D008970:Molecular Weight; D009419:Nerve Tissue Proteins; D010786:Photoreceptor Cells / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D051603:Recoverin; D064030:S100 Calcium Binding Protein G / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*
D000951:Antigens, Neoplasm; D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; D064030:S100 Calcium Binding Protein G; D051603:Recoverin; D051597:Hippocalcin