Number of transducin molecules that one single molecule of the light-activated receptor rhodopsin can turn over in intact rod cells

Range >3,000 transducins/rhodopsin
Organism Toad Bufo marinus
Reference Kahlert, M., and K. P. Hofmann. 1991. Reaction rate and collision efficiency of the rhodopsin-transducin system in intact retinal rods. Biophys. J. 59: 375–386 DOI :10.1016/S0006-3495(91)82231-7 p.375 left column bottom paragraphPubMed ID1901231
Primary Source Dawis, S. M., R. M. Graeff, R. A. Heyman, T. F. Walseth, and N. D. Goldberg. 1988. Regulation of cyclic GMP metabolism in toad photoreceptors. J. Biol. Chem. 263: 8771-8785.PubMed ID2837463
Method (From primary source:) "...the mechanisms subserving the regulation of photoreceptor cGMP metabolism were assessed in intact red rod photoreceptors of isolated toad retinas by examining metabolic responses to different photic stimuli."
Comments "...[researchers] have explored the dynamics of the activation reaction of the rod G-protein (transducin, Gt). In intact rod cells, one single molecule of the light-activated receptor rhodopsin (R*) can turn over >3,000 copies of Gt (primary source). The well-known fast lateral and rotational diffusion of rhodopsin, and presumably of Gt, in the disc membrane affords sufficiently frequent collisions for a high speed of activation."
Entered by Uri M
ID 110989