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  The contribution of a sensitizing pigment to the photosensitivity spectra of fly rhodopsin amd metarhodopsin

Minke, B., & Kirschfeld, K. (1979). The contribution of a sensitizing pigment to the photosensitivity spectra of fly rhodopsin amd metarhodopsin. Journal of General Physiology, 73(5), 517-540. doi:10.1085/jgp.73.5.517.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-F128-2 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-0B06-8
Genre: Journal Article

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 Creators:
Minke, B1, 2, Author              
Kirschfeld, K1, 2, Author              
Affiliations:
1Former Department Comparative Neurobiology, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497800              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497794              

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 Abstract: Most of the photoreceptors of the fly compound eye have high sensitivity in the ultraviolet (UV) as well as in the visible spectral range. This UV sensitivity arises from a photostable pigment that acts as a sensitizer for rhodopsin. Because the sensitizing pigment cannot be bleached, the classical determination of the photosensitivity spectrum from measurements of the difference spectrum of the pigment cannot be applied. We therefore used a new method to determine the photosensitivity spectra of rhodopsin and metarhodopsin in the UV spectral range. The method is based on the fact that the invertebrate visual pigment is a bistable one, in which rhodopsin and metarhodopsin are photointerconvertible. The pigment changes were measured by a fast electrical potential, called the M potential, which arises from activation of metarhodopsin. We first established the use of the M potential as a reliable measure of the visual pigment changes in the fly. We then calculated the photosensitivity spectrum of rhodopsin and metarhodopsin by using two kinds of experimentally measured spectra: the relaxation and the photoequilibrium spectra. The relaxation spectrum represents the wavelength dependence of the rate of approach of the pigment molecules to photoequilibrium. This spectrum is the weighted sum of the photosensitivity spectra of rhodopsin and metarhodopsin. The photoequilibrium spectrum measures the fraction of metarhodopsin (or rhodopsin) in photoequilibrium which is reached in the steady state for application of various wavelengths of light. By using this method we found that, although the photosensitivity spectra of rhodopsin and metarhodopsin are very different in the visible, they show strict coincidence in the UV region. This observation indicates that the photostable pigment acts as a sensitizer for both rhodopsin as well as metarhodopsin.

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 Dates: 1979-05
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: -
 Identifiers: BibTex Citekey: 3733
DOI: 10.1085/jgp.73.5.517
 Degree: -

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Title: Journal of General Physiology
  Other : J. Gen. Physiol.
  Abbreviation : JGP
Source Genre: Journal
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Affiliations:
Publ. Info: Rockefeller University Press
Pages: - Volume / Issue: 73 (5) Sequence Number: - Start / End Page: 517 - 540 Identifier: ISSN: 0022-1295
CoNE: https://pure.mpg.de/cone/journals/resource/954925413895