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  A Defective Proton Pump, Point-Mutated Bacteriorhodopsin Asp96 → Asn Is Fully Reactivated by Azide

Tittor, J., Soell, C., Oesterhelt, D., Butt, H. J., & Bamberg, E. (1989). A Defective Proton Pump, Point-Mutated Bacteriorhodopsin Asp96 → Asn Is Fully Reactivated by Azide. The EMBO Journal, 8(11), 3477-3482. doi:10.1002/j.1460-2075.1989.tb08512.x.

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 Creators:
Tittor, Jörg1, Author              
Soell, Christa1, Author
Oesterhelt, Dieter1, Author              
Butt, Hans J.2, Author              
Bamberg, Ernst2, Author              
Affiliations:
1Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society, ou_1565164              
2Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society, ou_2068289              

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Free keywords: Anions, Asparagine, Aspartic Acid, Azides, Bacteriorhodopsins, Biological Transport, Hydrogen-Ion Concentration, Mutation, Protons, Temperature, Thermodynamics
 Abstract: Addition of azide fully restored the proton pump activity of defective bacteriorhodopsin (BR) mutant protein Asp96 → Asn. The decay time of M of BR Asp96 → Asn, the longest living intermediate, was decreased from 500 ms at pH 7.0 to approximately 1 ms under conditions of saturating azide concentrations. This decay was faster than the decay of M in the wild-type, where no such azide effect was detectable. Stationary photocurrents, measured with purple membranes immobilized and oriented in a polyacrylamide gel, increased upon addition of azide up to the level of the wild-type. Different small anions of weak acids restored the pump activity with decreasing affinity in the order: cyanate greater than azide greater than nitrite greater than formiate greater than acetate. The activation energy of the M decay in the mutant was higher in the presence (48 kJ/mol) than in the absence (27 kJ/mol) of 100 mM azide even though the absolute rate was dramatically increased by azide. This effect of azide is due to the substitution of a carboxamido group for a carboxylic group at position 96 which removes the internal proton donor and causes an increase in the entropy change of activation for proton transfer which is reversed by azide.

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Language(s): eng - English
 Dates: 1989-06-2319891989-11
 Publication Status: Published in print
 Pages: 6
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: BibTex Citekey: tittor_defective_1989
DOI: 10.1002/j.1460-2075.1989.tb08512.x
PMID: 2555165
 Degree: -

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Title: The EMBO Journal
Source Genre: Journal
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Publ. Info: Nature Publishing Group
Pages: - Volume / Issue: 8 (11) Sequence Number: - Start / End Page: 3477 - 3482 Identifier: ISSN: 0261-4189
CoNE: https://pure.mpg.de/cone/journals/resource/954925497061_1