HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 275, Issue 28, 21010-21016, July 14, 2000

This Article Full Text Full Text (PDF) All Versions of this Article: 275/28/21010    most recent M001208200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Aharoni, A. Articles by Sheves, M. Search for Related Content PubMed PubMed Citation Articles by Aharoni, A. Articles by Sheves, M. Social Bookmarking                      What's this?

Bacteriorhodpsin Experiences Light-induced Conformational Alterations in Nonisomerizable C₁₃=C₁₄ Pigments
A STUDY WITH EPR^*

Amir Aharoni, Lev Weiner^§, Michael Ottolenghi^¶, and Mordechai Sheves

From the Departments of  Organic Chemistry and ^§ Chemical Services, The Weizmann Institute of Science, Rehovot 76100, Israel and the ^¶ Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

The mechanism by which bacteriorhodopsin is activated following light absorption is not completely clear. We have detected protein conformational alterations following light absorption by retinal-based chromophores in the bacteriorhodopsin binding site by monitoring the rate of reduction-oxidation reactions of covalently attached spin labels, using EPR spectroscopy. It was found that the reduction reaction with hydroxylamine is light-catalyzed in the A103C-labeled pigment but not in E74C or M163C. The reaction is light-catalyzed even when isomerization of the C₁₃=C₁₄ bond of the retinal chromophore is prevented. The reverse oxidation reaction with molecular oxygen is effective only in apomembrane derived from the mutant A103C. This reaction is light-accelerated following light absorption of the retinal oxime, which occupies the binding site. The light-induced acceleration is evident also in "locked" bacteriorhodopsin in which isomerization around the C₁₃=C₁₄ bond is prevented. It is evident that the chromophore-protein covalent bond is not a prerequisite for protein response. In contrast to the case of the retinal oxime, a reduced C=N bond A103C-labeled pigment did not exhibit acceleration of the oxidation reaction following light absorption. Acceleration was observed, however, following substitution of the polyene by groups that modify the excited state charge delocalization. It is suggested that protein conformational alterations are induced by charge redistribution along the retinal polyene following light absorption.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				F. J. Bartl, E. Ritter, and K. P. Hofmann Signaling States of Rhodopsin. ABSORPTION OF LIGHT IN ACTIVE METARHODOPSIN II GENERATES AN ALL-TRANS-RETINAL BOUND INACTIVE STATE J. Biol. Chem., August 3, 2001; 276(32): 30161 - 30166. [Abstract] [Full Text] [PDF]