Document Detail


Structure-function relationships in diphtheria toxin channels: III. Residues which affect the cis pH dependence of channel conductance.
MedLine Citation:
PMID:  7516434     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The conductance of channels formed by diphtheria toxin (DT) in lipid bilayer membrane depends strongly on pH. We have previously shown that a 61 amino acid region of the protein, denoted TH8-9, is sufficient to form channels having the same pH-dependent conductance properties as those of whole toxin channels. One residue in this region, Aspartate 352, is responsible for all the dependence of single channel conductance on trans pH, whereas another, Glutamate 349, has no effect. Here, we report that of the seven remaining charged residues in the TH8-9 region, mutations altering the charge on H322, H323, H372, and R377 have minimal effects on single channel conductance; mutations of Glutamates 326, 327, or 362, however, significantly affect single channel conductance as well as its dependence on cis pH. Moreover, Glutamate 362 is titratable from both the cis and trans sides of the membrane, suggesting that this residue lies within the channel; it is more accessible, however, to cis than to trans protons. These results are consistent with the membrane-spanning topology previously proposed for the TH8-9 region, and suggest a geometric model for the DT channel.
Authors:
J A Mindell; J A Silverman; R J Collier; A Finkelstein
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of membrane biology     Volume:  137     ISSN:  0022-2631     ISO Abbreviation:  J. Membr. Biol.     Publication Date:  1994 Jan 
Date Detail:
Created Date:  1994-07-19     Completed Date:  1994-07-19     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0211301     Medline TA:  J Membr Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  45-57     Citation Subset:  IM    
Affiliation:
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461.
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MeSH Terms
Descriptor/Qualifier:
Aspartic Acid / analysis
Diphtheria Toxin* / analysis,  metabolism,  physiology
Glutamates / analysis
Glutamic Acid
Hydrogen-Ion Concentration
Ion Channels / chemistry*,  physiology*,  ultrastructure
Lipid Bilayers / chemistry
Membrane Potentials / physiology*
Membranes, Artificial
Mutation
Structure-Activity Relationship
Grant Support
ID/Acronym/Agency:
AI22021/AI/NIAID NIH HHS; AI22848/AI/NIAID NIH HHS; T32 GM07288/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
0/Diphtheria Toxin; 0/Glutamates; 0/Ion Channels; 0/Lipid Bilayers; 0/Membranes, Artificial; 56-84-8/Aspartic Acid; 56-86-0/Glutamic Acid

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