Abstract
We present the results of a theoretical analysis of a completely general linear chain model for transduction in photoreceptors from which we have derived a statistical test for the intrinsic linearity of the single-photon transduction process. By linearity we mean comprising first-order chemical reactions only. We show results of our own measurements in Limulus ventral photoreceptors that pass this linearity test, suggesting that the single-photon transduction in Limulus may be a simple chain of first-order biochemical reactions (plus possible diffusional processes). However, we also demonstrate that published data show the existence of strong nonlinearities in the single-photon responses of toad and perhaps also of locust. Such nonlinearities are not difficult to construct from existing biochemical notions (feedback, cooperativity), but all but one [Kramer, L. (1975) Biophys. Struct. Mech. 1,239-257] of the published analytical models of the single-photon process have been linear. The test we have used is the distribution of "areas" (time integrals of conductance changes) of single-photon responses or "bumps." Reasonable molecular linear chain models do not allow distributions very sharply peaked at non-zero values. Such peaked distributions are seen in toad and locust but not in Limulus.
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Selected References
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- Baylor D. A., Lamb T. D., Yau K. W. Responses of retinal rods to single photons. J Physiol. 1979 Mar;288:613–634. [PMC free article] [PubMed] [Google Scholar]
- Borsellino A., Fuortes M. G. Responses to single photons in virual cells of limulus. J Physiol. 1968 Jun;196(3):507–539. doi: 10.1113/jphysiol.1968.sp008521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brown J. E., Coles J. A. Saturation of the response to light in Limulus ventral photoreceptor. J Physiol. 1979 Nov;296:373–392. doi: 10.1113/jphysiol.1979.sp013011. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dodge F. A., Jr, Knight B. W., Toyoda J. Voltage noise in Limulus visual cells. Science. 1968 Apr 5;160(3823):88–90. doi: 10.1126/science.160.3823.88. [DOI] [PubMed] [Google Scholar]
- Katz G. M., Schwartz T. L. Temporal control of voltage-clamped membranes: an examination of principles. J Membr Biol. 1974 Jul 12;17(3):275–291. doi: 10.1007/BF01870188. [DOI] [PubMed] [Google Scholar]
- Kühn H., Cook J. H., Dreyer W. J. Phosphorylation of rhodopsin in bovine photoreceptor membranes. A dark reaction after illumination. Biochemistry. 1973 Jun 19;12(13):2495–2502. doi: 10.1021/bi00737a020. [DOI] [PubMed] [Google Scholar]
- Liebman P. A., Pugh E. N., Jr The control of phosphodiesterase in rod disk membranes: kinetics, possible mechanisms and significance for vision. Vision Res. 1979;19(4):375–380. doi: 10.1016/0042-6989(79)90097-x. [DOI] [PubMed] [Google Scholar]
- Lisman J. E., Brown J. E. Light-induced changes of sensitivity in Limulus ventral photoreceptors. J Gen Physiol. 1975 Oct;66(4):473–488. doi: 10.1085/jgp.66.4.473. [DOI] [PMC free article] [PubMed] [Google Scholar]