Activation of retinal rod cyclic GMP-phosphodiesterase by transducin: characterization of the complex formed by phosphodiesterase inhibitor and transducin alpha-subunit.
The GTP-binding subunit of transducin (T alpha) activates the cGMP phosphodiesterase (PDE) of bovine retinal rods by relieving the constraint imposed by the inhibitory subunit PDE gamma. We have isolated and characterized the complex T alpha.GTP gamma S-PDE gamma formed when T alpha is activated by the nonhydrolyzable analog GTP gamma S. Sedimentation and light-scattering techniques demonstrate that, in contrast to free T alpha.GTP gamma S, which is soluble, the T alpha.GTP gamma S-PDE gamma complex, as well as T alpha.GTP-PDE gamma, is membrane bound at cytosolic ionic strength. It is eluted from the membrane at low ionic strength as a monomeric and 1:1 stoichiometric complex. The relative affinities of PDE gamma for PDE alpha beta and for T alpha.GTP are discussed.
Deterre
P
P
Laboratoire de Biophysique Moléculaire et Cellulaire (Unité Associée 520 du CNRS), DRF-CEN Grenoble, France.
Bigay
J
J
Robert
M
M
Pfister
C
C
Kühn
H
H
Chabre
M
M
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000378:metabolism; D066298:In Vitro Techniques; D008027:Light; D008565:Membrane Proteins / Q000378:metabolism / Q000494:pharmacology*; D008566:Membranes / Q000378:metabolism; D010786:Photoreceptor Cells / Q000201:enzymology*; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D012542:Scattering, Radiation; D015293:Transducin
D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D015293:Transducin