Activation of the bovine retinal rod outer segment cGMP-specific phosphodiesterase by the transducin-GTP[S] complex in a physiologically significant range of free calcium ion concentrations
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The basal- and GTP[S]-stimulated activities of cGMP-specific phosphodiesterase were measured in totally bleached bovine retinal rod outer segments suspensions at high and low free calcium ions concentration (≈100 μM and <10 nM, respectively). The obtained results suggest that the activity of free phosphodiesterase in rod outer segment membranes and all following processes (transducin activation, interaction transducin-GTP[S] complex with phosphodiesterase, and activity of the enzyme stimulated by transducin-GTP[S] complex) do not depend on the concentration of free calcium ions in a physiologically significant range of its concentration changes in rod outer segments.
Keywordsphotoreceptor phosphodiesterase transducin-induced activation calcium ions
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