Document Detail


Substitution of membrane-embedded aspartic acids in bacteriorhodopsin causes specific changes in different steps of the photochemical cycle.
MedLine Citation:
PMID:  2575917     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Millisecond photocycle kinetics were measured at room temperature for 13 site-specific bacteriorhodopsin mutants in which single aspartic acid residues were replaced by asparagine, glutamic acid, or alanine. Replacement of aspartic acid residues expected to be within the membrane-embedded region of the protein (Asp-85, -96, -115, or -212) produced large alterations in the photocycle. Substitution of Asp-85 or Asp-212 by Asn altered or blocked formation of the M410 photointermediate. Substitution of these two residues by Glu decreased the amount of M410 formed. Substitutions of Asp-96 slowed the decay rate of the M410 photointermediate, and substitutions of Asp-115 slowed the decay rate of the O640 photointermediate. Corresponding substitutions of aspartic acid residues expected to be in cytoplasmic loop regions of the protein (Asp-36, -38, -102, or -104) resulted in little or no alteration of the photocycle. Our results indicate that the defects in proton pumping which we have previously observed upon substitution of Asp-85, Asp-96, Asp-115, and Asp-212 [Mogi, T., Stern, L. J., Marti, T., Chao, B. H., & Khorana, H. G. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 4148-4152] are closely coupled to alterations in the photocycle. The photocycle alterations observed in these mutants are discussed in relation to the functional roles of specific aspartic acid residues at different stages of the bacteriorhodopsin photocycle and the proton pumping mechanism.
Authors:
L J Stern; P L Ahl; T Marti; T Mogi; M Duñach; S Berkowitz; K J Rothschild; H G Khorana
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  28     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1989 Dec 
Date Detail:
Created Date:  1990-03-27     Completed Date:  1990-03-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  10035-42     Citation Subset:  IM    
Affiliation:
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139.
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MeSH Terms
Descriptor/Qualifier:
Alanine
Amino Acid Sequence
Asparagine
Aspartic Acid / metabolism*
Bacteriorhodopsins / metabolism*
Cell Membrane / metabolism*
Glutamates
Glutamic Acid
Hydrogen-Ion Concentration
Kinetics
Lipid Bilayers / metabolism
Molecular Sequence Data
Mutation
Photochemistry
Grant Support
ID/Acronym/Agency:
AI11479/AI/NIAID NIH HHS; GM28289-09/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
0/Glutamates; 0/Lipid Bilayers; 53026-44-1/Bacteriorhodopsins; 56-41-7/Alanine; 56-84-8/Aspartic Acid; 56-86-0/Glutamic Acid; 7006-34-0/Asparagine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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