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  Proton translocation by bacteriorhodopsin in the absence of substantial conformational changes

Tittor, J., Paula, S., Subramaniam, S., Heberle, J., Henderson, R., & Oesterhelt, D. (2002). Proton translocation by bacteriorhodopsin in the absence of substantial conformational changes. Journal of Molecular Biology, 319(2), 555-565.

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Genre: Journal Article
Alternative Title : J. Mol. Biol.

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 Creators:
Tittor, J.1, 2, Author              
Paula, S., Author
Subramaniam, S., Author
Heberle, J., Author
Henderson, R., Author
Oesterhelt, D.1, Author              
Affiliations:
1Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society, ou_1565164              
2Conti, Elena / Structural Cell Biology, Max Planck Institute of Biochemistry, Max Planck Society, ou_1565144              

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Free keywords: retinal protein; photocycle; spectroscopy; vectorial catalysis
 Abstract: Unlike wild-type bacteriorhodopsin (BR), the BR triple mutant D96G/F171C/F219L has been shown to undergo only minor structural rearrangements during its photocycle. Nonetheless, the mutant is capable of transporting protons at a rate of 125(+/-40) H+/BR per minute under light-saturating conditions. Light adaptation of the triple mutant's retinal proceeds in a pH-dependent manner LIP to a maximum of 63%, all-trans. These two findings imply that the transport activity of the triple mutant comprises 66% of the wild-type activity. Time-resolved spectroscopy reveals that the identity and sequence of intermediates in the photocycle of the triple mutant in the all-trans configuration correspond to that of wild-type BR. The only differences relate to a slower rise and decay of the M and O intermediates, and a significant spectral contribution from a 13-cis component. No indication for accumulation of the N intermediate is found under a variety of conditions that normally favor the formation of this species in wild-type BR. The Fourer transform infrared (FTIR) spectrum of the M intermediate in the triple mutant resembles that of wild type. Minor changes in the amide I region during the photocycle suggest that only small movements of the protein backbone occur. Electron microscopy reveals large differences in conformation between the unilluminated state of the mutant protein and wild-type but no light-induced changes in time- resolved measurements. Evidently, proton transport by the triple mutant does not require the major conformational rearrangements that occur on the same time-scale with wild- type. Thus, we conclude that large conformational changes observed in the photocycle of the wild-type and many BR mutants are not a prerequisite for the change in accessibility of the Schiff base nitrogen atom that must occur during vectorial catalysis to allow, proton transport. (C) 2002 Elsevier Science Ltd. All rights reserved.

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Language(s): eng - English
 Dates: 2002-05-31
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 29174
ISI: 000176229100025
 Degree: -

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Title: Journal of Molecular Biology
  Alternative Title : J. Mol. Biol.
Source Genre: Journal
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Pages: - Volume / Issue: 319 (2) Sequence Number: - Start / End Page: 555 - 565 Identifier: ISSN: 0022-2836