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Comparative analysis of the orientation of transmembrane peptides using solid-state (2)H- and (15)N-NMR: mobility matters.
MedLine Citation:
PMID:  22453992     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Many solid-state nuclear magnetic resonance (NMR) approaches for membrane proteins rely on orientation-dependent parameters, from which the alignment of peptide segments in the lipid bilayer can be calculated. Molecules embedded in liquid-crystalline membranes, such as monomeric helices, are highly mobile, leading to partial averaging of the measured NMR parameters. These dynamic effects need to be taken into account to avoid misinterpretation of NMR data. Here, we compare two common NMR approaches: (2)H-NMR quadrupolar waves, and separated local field (15)N-(1)H polarization inversion spin exchange at magic angle (PISEMA) spectra, in order to identify their strengths and drawbacks for correctly determining the orientation and mobility of α-helical transmembrane peptides. We first analyzed the model peptide WLP23 in oriented dimyristoylphosphatidylcholine (DMPC) membranes and then contrasted it with published data on GWALP23 in dilauroylphosphatidylcholine (DLPC). We only obtained consistent tilt angles from the two methods when taking dynamics into account. Interestingly, the two related peptides differ fundamentally in their mobility. Although both helices adopt the same tilt in their respective bilayers (~20°), WLP23 undergoes extensive fluctuations in its azimuthal rotation angle, whereas GWALP23 is much less dynamic. Both alternative NMR methods are suitable for characterizing orientation and dynamics, yet they can be optimally used to address different aspects. PISEMA spectra immediately reveal the presence of large-amplitude rotational fluctuations, which are not directly seen by (2)H-NMR. On the other hand, PISEMA was unable to define the azimuthal rotation angle in the case of the highly dynamic WLP23, though the helix tilt could still be determined, irrespective of any dynamics parameters.
Authors:
Stephan L Grage; Erik Strandberg; Parvesh Wadhwani; Santiago Esteban-Martín; Jesús Salgado; Anne S Ulrich
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-3-28
Journal Detail:
Title:  European biophysics journal : EBJ     Volume:  -     ISSN:  1432-1017     ISO Abbreviation:  -     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-3-28     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8409413     Medline TA:  Eur Biophys J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Institute for Biological Interfaces (IBG-2) and Institute of Organic Chemistry and CFN, Karlsruhe Institute of Technology, P.O. Box 3640, 76021, Karlsruhe, Germany.
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