help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Laitko, U.
Right arrow Articles by Hofmann, K. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Laitko, U.
Right arrow Articles by Hofmann, K. P.

Biophys J, February 1998, p. 803-815, Vol. 74, No. 2

A Model for the Recovery Kinetics of Rod Phototransduction, Based on the Enzymatic Deactivation of Rhodopsin

U. Laitko and K. P. Hofmann

Institut für Medizinische Physik und Biophysik, Medizinische Fakultät Charité der Humboldt-Universität zu Berlin, D-10098 Berlin, Germany

We propose a model for the recovery of the retinal rod photoresponse after a short stimulus. The approach describes the enzymatic deactivation of the photoactivated receptor, rhodopsin, by simple enzyme kinetics. An important feature of this description is that the R* deactivation obeys different time laws, depending on the numbers of R* formed per disc membrane and available enzyme molecules. If the enzyme works below substrate saturation, the rate of deactivation depends linearly on the number of R*, whereas for substrate saturation a hyperbolic relation---the well-known Michaelis-Menten equation---applies. This dichotomy is used to explain experimental finding that the relation between the saturation time of the photoresponse after short illumination and the flash strength has two sharply separated branches for low and high flash intensities (up to ~10% bleaching). By relating both branches to properties of the enzymatic rhodopsin deactivation, the new model transcends the classical notion of a constant characteristic lifetime of activated rhodopsin. With parameters that are plausible in the light of the available data and the additional information that the deactivating enzyme, rhodopsin kinase, and the signaling G-protein, transducin, compete for the active receptor, the slopes of the saturation function are correctly reproduced.

Biophys J, February 1998, p. 803-815, Vol. 74, No. 2
© 1998 by the Biophysical Society   0006-3495/98/02/803/13  $2.00


This article has been cited by other articles:


Home page
 J. Biol. Chem.Home page
G. W. Shi, J. Chen, F. Concepcion, K. Motamedchaboki, P. Marjoram, R. Langen, and J. Chen
Light Causes Phosphorylation of Nonactivated Visual Pigments in Intact Mouse Rod Photoreceptor Cells
J. Biol. Chem., December 16, 2005; 280(50): 41184 - 41191.
[Abstract] [Full Text] [PDF]

Home page
 IOVSHome page
M. J. Kennedy, M. E. Sowa, T. G. Wensel, and J. B. Hurley
Acceleration of Key Reactions as a Strategy to Elucidate the Rate-Limiting Chemistry Underlying Phototransduction Inactivation
Invest. Ophthalmol. Vis. Sci., March 1, 2003; 44(3): 1016 - 1022.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
M. H. Hennig, K. Funke, and F. Worgotter
The Influence of Different Retinal Subcircuits on the Nonlinearity of Ganglion Cell Behavior
J. Neurosci., October 1, 2002; 22(19): 8726 - 8738.
[Abstract] [Full Text] [PDF]

Home page
 Proc. Natl. Acad. Sci. USAHome page
F. Dicker, U. Quitterer, R. Winstel, K. Honold, and M. J. Lohse
Phosphorylation-independent inhibition of parathyroid hormone receptor signaling by G protein-coupled receptor kinases
PNAS, May 11, 1999; 96(10): 5476 - 5481.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1998 by the Biophysical Society.