A GTPase-accelerating factor for transducin, distinct from its effector cGMP phosphodiesterase, in rod outer segment membranes

• Published in: Neuron (Cambridge, Mass.) Vol. 11; no. 5; pp. 939 - 949
• Main Authors: Angleson, Joseph K., Wensel, Theodore G.
• Format: Journal Article
• Language: English
• Published: Cambridge, MA Elsevier Inc 01.11.1993; Cell Press
• Subjects: 3',5'-Cyclic-GMP Phosphodiesterases - metabolism; Animals; Biological and medical sciences; Cattle; Enzyme Activation - drug effects; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; GTPase-Activating Proteins; Guanosine Triphosphate - metabolism; Hydrolysis; Kinetics; Membranes - metabolism; Phosphodiesterase Inhibitors - pharmacology; Phosphoric Diester Hydrolases - pharmacology; Proteins - metabolism; Rod Cell Outer Segment - metabolism; Transducin - metabolism; Vertebrates: nervous system and sense organs; GTP; Enzyme; Triphosphoric monoester hydrolases; 3',5'-Cyclic-GMP phosphodiesterase; Photoreceptor; Transducin; dGTPase; Retina; Ox; Esterases; Phosphoric diester hydrolases; Eye; Hydrolysis; Visual system; Signal transduction; Vertebrata; Mammalia; Outer segment; Hydrolases; Membrane; Artiodactyla; Kinetics; Ungulata; G protein
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/0896-6273(93)90123-9

Hydrolysis of GTP by the photoreceptor G protein transducin (G tα) was found to occur with kinetics identical to the inactivation of its effector cGMP phosphodiesterase (PDE), but was too slow (tens of seconds) in dilute rod outer segment (ROS) suspensions to account for subsecond recovery of the light response. Raising the concentration of ROS membranes increased the rates of GTP hydrolysis and PDE inactivation in parallel as much as 6-fold. Holo-PDE and its γ subunit had weak effects on GTPase kinetics (<1.6-fold and <1.3-fold, respectively). ROS membranes stripped of PDE retained ∼90% of a GTPase accelerating activity that was protease sensitive, indicating that they contain a GTPase-accelerating factor distinct from PDE.