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Transducin GTPase provides for rapid quenching of the cGMP cascade in rod outer segments
Author(s) -
Arshavsky V.Yu.,
Antoch M.P.,
Lukjanov K.A.,
Philippov P.P.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80754-9
Subject(s) - transducin , gtpase , phosphodiesterase , quenching (fluorescence) , gtp' , biophysics , chemistry , biochemistry , g protein , biology , enzyme , physics , signal transduction , fluorescence , optics
The role of transducin GTPase in rapid cGMP phosphodiesterase quenching was studied by simultaneous registration of GTP hydrolysis and phosphodiesterase activity in the same rod outer segments (ROS) preparation. The results thus obtained allow the conclusion that: (i) phosphodiesterase quenching coincides with transducin‐bound GTP hydrolysis independently of ROS concentration; (ii) an increase in the ROS concentration results in the acceleration of cascade quenching due to the existence of a GTPase accelerating mechanism in ROS; (iii) approximation to physiological conditions (protein concentration, temperature) provides a transducin GTPase rate equal to 1–2 turnovers per second i.e., sufficiently high for satisfying the real rate of photoresponse reversion in dark‐adapted rods.