A novel calcium-dependent activator of retinal rod outer segment membrane guanylate cyclase.
The membrane guanylate cyclase in retinal rod outer segments (ROS-GC) is known to be negatively regulated by calcium; when the calcium concentration is reduced below the dark-adapted level of about 500 nM, the enzyme is activated by a soluble protein. We now report that the enzyme is also positively regulated by calcium; a novel soluble protein is identified and purified from bovine retina which activates ROS-GC, with half-maximal activation occurring at 2-5 microM calcium. The activation is dose-dependent, and at its maximum, cyclase is stimulated up to 25-fold. The activator has a molecular mass of about 40 kDa and is a multimer of a 6-7 kDa peptide.
Pozdnyakov
N
N
Eye Research Institute, Oakland University, Rochester, Michigan 48309, USA.
Yoshida
A
A
Cooper
N G
NG
Margulis
A
A
Duda
T
T
Sharma
R K
RK
Sitaramayya
A
A
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002417:Cattle; D006224:Cricetinae; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D014162:Transfection
D002135:Calcium-Binding Proteins; D006162:Guanylate Cyclase; D002118:Calcium