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On the role of transducin GTPase in the quenching of a phosphodiesterase cascade of vision
Author(s) -
Arshavsky V.Yu.,
Antoch M.P.,
Philippov P.P.
Publication year - 1987
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(87)80414-3
Subject(s) - transducin , phosphodiesterase , gtpase , gtp' , biophysics , quenching (fluorescence) , chemistry , g protein , biochemistry , hydrolysis , reaction rate constant , stereochemistry , enzyme , biology , kinetics , signal transduction , physics , quantum mechanics , fluorescence
The rate of GTP hydrolysis in the active site of transducin and that of the release of the phosphate thus formed have been measured. The former step has been found to be a rate‐limiting one. The rate constant for GTP hydrolysis is equal to 0.027 s −1 at 23°C, and 0.07 s −1 at 37°C. Bedsides, it has been shown that the rate of GTPase reaction on the transducin α‐subunit does not depend on the concentration of a complex of transducin β‐ and γ‐subunits or on the presence of cGMP phosphodiesterase and a 48 kDa protein from rod outer segments. According to the results, GTP hydrolysis on transducin proceeds too slowly to account for the rapid quenching of a phosphodiesterase cascade in rod outer segments.