[Effect of GDP on transducin interaction with cyclic nucleotide phosphodiesterase and rhodopsin from bovine retinal rods].
In the presence of guanyl nucleotides and rhodopsin-containing retinal rod outer segment membranes, transducin stimulates the light-sensitive cyclic nucleotide phosphodiesterase 5.5-7 times. The activation constant (Ka) for GTP and Gpp(NH)p is 0.25 microM, that for GDP and GDP beta S is 14 and 110 microM, respectively. GDP purified from other nucleotide contaminations at concentrations up to 1 mM does not stimulate phosphodiesterase but binds to transducin and inhibits the Gpp(NH)p-dependent activation of phosphodiesterase. The mode of transducin interaction with bleached rhodopsin also depends on the nature of the bound guanyl nucleotide: in the presence of GDP rhodopsin-containing membranes bind 70-100% of transducin, whereas in the presence of Gpp(NH)p the membranes bind only 13% of the protein. The experimental results suggest that GDP and GTP convert transducin into two different functional states, i.e., the transducin X GTP complex binds to phosphodiesterase causing its stimulation, while the transducin X GDP complex is predominantly bound to rhodopsin.
D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004789:Enzyme Activation; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000378:metabolism*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000201:enzymology / Q000378:metabolism*; D015293:Transducin
D006150:Guanine Nucleotides; D008565:Membrane Proteins; D006153:Guanosine Diphosphate; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D015293:Transducin
Vliianie GDP na vzaimodeĭstvie transdutsina s fosfoésterazoĭ tsiklicheskikh nukleotidov i rodopsinom palochek setchatki byka.