Single cyclic GMP-activated channel activity in excised patches of rod outer segment membrane

Nature ◽  
1986 ◽  
Vol 321 (6065) ◽  
pp. 66-70 ◽  
Author(s):  
L. W. Haynes ◽  
A. R. Kay ◽  
K.-W. Yau
Keyword(s):  
Cyclic Gmp ◽  
Outer Segment ◽  
Channel Activity ◽  
Rod Outer Segment ◽  
Excised Patches

scholarly journals The effect of the γ-subunit of the cyclic GMP phosphodiesterase of bovine and frog (Rana catesbiana) retinal rod outer segments on the kinetic parameters of the enzyme

1990 ◽  
Vol 265 (3) ◽  
pp. 655-658 ◽  
Author(s):  
M M Whalen ◽  
M W Bitensky ◽  
D J Takemoto
Keyword(s):  
Catalytic Activity ◽  
Cyclic Gmp ◽  
Active Sites ◽  
Outer Segment ◽  
Maximal Activity ◽  
Inhibitory Effect ◽  
Gamma Subunit ◽  
Rod Outer Segment ◽  
Gamma Subunits ◽  
Alpha Beta

Rod-outer-segment cyclic GMP phosphodiesterase (PDE) (subunit composition alpha beta gamma 2) contains catalytic activity in alpha beta. The gamma-subunits are inhibitors. Removal of the gamma-subunits increases Vmax. without affecting the Km. The inhibitory effect of a single gamma-subunit (alpha beta gamma) on the Vmax. of alpha beta is much greater in bovine than in frog (Rana catesbiana) PDE. Bovine PDE in the alpha beta gamma 2 state has a Vmax. that is 2.6 +/- 0.4% of the Vmax. of alpha beta. The removal of one gamma-subunit to give alpha beta gamma results in a Vmax. 5.2 +/- 1% of that for maximal activity. Frog alpha beta gamma 2 has a Vmax. 10.8 +/- 2%, and alpha beta gamma has a Vmax. 50 +/- 18%, of the Vmax. of alpha beta. These data suggest that a single gamma-subunit can inhibit the catalytic activity of active sites on both alpha- and beta-subunits in bovine, but not in frog, rod-outer-segment PDE.

scholarly journals Structural and functional characterization of the rod outer segment membrane guanylate cyclase

1994 ◽  
Vol 302 (2) ◽  
pp. 455-461 ◽  
Author(s):  
R M Goraczniak ◽  
T Duda ◽  
A Sitaramayya ◽  
R K Sharma
Keyword(s):  
Cyclic Gmp ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Functional Characterization ◽  
Visual Signal ◽  
Membrane Guanylate Cyclase ◽  
Rod Outer Segment ◽  
Vertebrate Photoreceptor ◽  
Hydrolysis Of

In the vertebrate photoreceptor cell, rod outer segment (ROS) is the site of visual signal-transduction process, and a pivotal molecule that regulates this process is cyclic GMP. Cyclic GMP controls the cationic conductance into the ROS, and light causes a decrease in the conductance by activating hydrolysis of the cyclic nucleotide. The identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown. We now report the cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC.

Rod outer segment phosphodiesterase: Factors affecting the hydrolysis of cyclic-AMP and cyclic-GMP

1974 ◽  
Vol 18 (6) ◽  
pp. 509-515 ◽  
Author(s):  
G. Chader ◽  
R. Fletcher ◽  
M. Johnson ◽  
R. Bensinger
Keyword(s):  
Cyclic Amp ◽  
Cyclic Gmp ◽  
Outer Segment ◽  
Factors Affecting ◽  
Rod Outer Segment ◽  
Hydrolysis Of

scholarly journals A derivative of amiloride blocks both the light-regulated and cyclic GMP-regulated conductances in rod photoreceptors.

1987 ◽  
Vol 90 (5) ◽  
pp. 651-669 ◽  
Author(s):  
G D Nicol ◽  
P P Schnetkamp ◽  
Y Saimi ◽  
E J Cragoe ◽  
M D Bownds
Keyword(s):  
Plasma Membrane ◽  
Cyclic Gmp ◽  
Dark Current ◽  
Outer Segment ◽  
Light Response ◽  
Ionic Channels ◽  
Rod Photoreceptors ◽  
Low Concentrations ◽  
Excised Patches ◽  
Activated Flux

Vertebrate rod photoreceptors in the dark maintain an inward current across the outer segment membrane. The photoresponse results from a light-induced suppression of this dark current. The light-regulated current is not sensitive to either tetrodotoxin or amiloride, potent blockers of Na+ channels. Here, we report that a derivative of amiloride, 3',4'-dichlorobenzamil (DCPA), completely suppresses the dark current and light response recorded from rod photoreceptors. DCPA also blocks a cyclic GMP-activated current in excised patches of rod plasma membrane and a cGMP-induced Ca++ flux from rod disk membranes. These results are consistent with the notion that the Ca++ flux mechanism in the disk membrane and the light-regulated conductance in the plasma membrane are identical. DCPA also inhibits the Na/Ca exchange mechanism in intact rods, but at a 5-10-fold-higher concentration than is required to block the cGMP-activated flux and current. The blocking action of DCPA in 10 nM Ca++ is different from that in 1 mM Ca++, which suggests either that the conductance state of the light-regulated channel may be modified in high and low concentrations of Ca++, or that there may be two ionic channels in the rod outer segment membrane.

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