Document Detail

Tidal surge in the M2 proton channel, sensed by 2D IR spectroscopy.
MedLine Citation:
PMID:  21444789     Owner:  NLM     Status:  MEDLINE    
The M2 proton channel from influenza A virus transmits protons across membranes via a narrow aqueous pore lined by water and a proton sensor, His37. Near the center of the membrane, a water cluster is stabilized by the carbonyl of Gly34 and His37, the properties of which are modulated by protonation of His37. At low pH (5-6), where M2 conducts protons, this region undergoes exchange processes on the microsecond to second timescale. Here, we use 2D IR to examine the instantaneous conformational distribution and hydration of G34, and the evolution of the ensemble on the femtosecond to picosecond timescale. The channel water is strongly pH dependent as gauged by 2D IR which allows recording of the vibrational frequency autocorrelation function of a (13)C = (18)O Gly34 probe. At pH 8, where entry and exit of protons within the channel are very slow, the carbonyl groups appear to adopt a single conformation/environment. The high-pH conformer does not exhibit spectral dynamics near the Gly34, and water in the channel must form a relatively rigid ice-like structure. By contrast, two vibrational forms of G34 are seen at pH 6.2, neither of which is identical to the high-pH form. In at least one of these low-pH forms, the probe is immersed in a very mobile, bulk-like aqueous environment having a correlation time ca. 1.3 ps at pH 6.2. Thus, protonation of His37 at low pH causes liquid-like water molecules to flow into the neighborhood of the Gly34.
Ayanjeet Ghosh; Jade Qiu; William F DeGrado; Robin M Hochstrasser
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2011-03-28
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  108     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-04-13     Completed Date:  2011-06-27     Revised Date:  2013-06-30    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  6115-20     Citation Subset:  IM    
Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
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MeSH Terms
Amino Acid Sequence
Amino Acid Substitution
Aspartic Acid / chemistry,  genetics
Hydrogen-Ion Concentration
Molecular Sequence Data
Protein Conformation
Spectrophotometry, Infrared
Viral Matrix Proteins / chemistry*,  genetics
Water / chemistry*
Grant Support
Reg. No./Substance:
0/M2 protein, Influenza A virus; 0/Protons; 0/Viral Matrix Proteins; 56-84-8/Aspartic Acid; 7732-18-5/Water

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

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