Solvent Effects on the Conformation of the Transmembrane Peptide Gramicidin A: Insights from Electrospray Ionization Mass Spectrometry

Bouchard, Mario; Benjamin, Dennis R.; Tito, Paula; Robinson, Carol V.; Dobson, Christopher M.

doi:10.1016/s0006-3495(00)76659-8

Cited by 27 publications

(29 citation statements)

References 44 publications

(60 reference statements)

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“…Folding Preference of 1-Me-Trp gA Analogues-Gramicidin A can adopt different structural conformations depending on different solvent environments (51,59). There are two major groups of conformers with different folding patterns.…”

Section: Discussionmentioning

confidence: 99%

The Preference of Tryptophan for Membrane Interfaces

Sun

Greathouse

Andersen

et al. 2008

Journal of Biological Chemistry

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To better understand the structural and functional roles of tryptophan at the membrane/water interface in membrane proteins, we examined the structural and functional consequences of Trp 3 1-methyl-tryptophan substitutions in membranespanning gramicidin A channels. Gramicidin A channels are miniproteins that are anchored to the interface by four Trps near the C terminus of each subunit in a membrane-spanning dimer. We masked the hydrogen bonding ability of individual or multiple Trps by 1-methylation of the indole ring and examined the structural and functional changes using circular dichroism spectroscopy, size exclusion chromatography, solid state 2 H NMR spectroscopy, and single channel analysis. N-Methylation causes distinct changes in the subunit conformational preference, channel-forming propensity, single channel conductance and lifetime, and average indole ring orientations within the membrane-spanning channels. The extent of the local ring dynamic wobble does not increase, and may decrease slightly, when the indole NH is replaced by the non-hydrogen-bonding and more bulky and hydrophobic N-CH 3 group. The changes in conformational preference, which are associated with a shift in the distribution of the aromatic residues across the bilayer, are similar to those observed previously with Trp 3 Phe substitutions. We conclude that indole N-H hydrogen bonding is of major importance for the folding of gramicidin channels. The changes in ion permeability, however, are quite different for Trp 3 Phe and Trp 3 1-methyl-tryptophan substitutions, indicating that the indole dipole moment and perhaps also ring size and are important for ion permeation through these channels.

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Section: Discussionmentioning

confidence: 99%

The Preference of Tryptophan for Membrane Interfaces

Sun

Greathouse

Andersen

et al. 2008

Journal of Biological Chemistry

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“…We further verifi ed the conformational change of TM-MHC-II. As the conformation of TM peptide varies in different solvents ( 38 ) and TFE can mimic the membranelike environment ( 39 ), we studied the secondary structure of NBD-cholesterol increased fl uorescence intensity, which then reached a plateau; the K d value for TM-MHC-II was 31 nM in presence of CHAPS ( Fig. 5B ).…”

Section: Cholesterol Changes Conformation Of Tm-mhc-iimentioning

confidence: 99%

Cholesterol lowering drug may influence cellular immune response by altering MHC II function

Roy

Ghosh

Pal

et al. 2013

Journal of Lipid Research

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There is a report that lowering of membrane cholesterol decreases expansion of the immune repertoire of CD4 + T cells, but not CD8 + T cells, in the thymic organ culture ( 3 ). The association of MHC II with either lipid raft or tetraspanin membrane domain is essential for effective antigen presentation ( 4,5 ). The treatment of antigen-presenting cells (APCs) with methyl ␤ -cyclodextrin (m ␤ -CD), known to deplete cellular cholesterol ( 6 ), reduces the antigen-presenting ability of MHC II without altering cell surface expression of MHC II ( 4 ). MHC II-restricted cognate interaction between APCs and CD4 + T cells is necessary for the initiation and propagation of immune response ( 7 ). Collectively the above information inclined to indicate that membrane cholesterol may play a decisive role in the expansion and maintenance of the immune repertoire, but the mechanism is largely unknown. This work is designed to understand how membrane cholesterol infl uences immune response.Cholesterol is important for lipid raft assembly ( 8 ) and also important for the formation of a tetraspanin-enriched microdomain ( 9 ). At a low cholesterol concentration, the diffusion coeffi cient of GPI-linked MHC II is reduced by a factor of 190 ( 10 ). There is a report that cholesterol depletion from the cell decreases the binding of anti-CCR5 antibodies directed to different sites of the receptor in a varying degree ( 11 ) The cholesterol lowering drug, statin, is extensively used in medical practice. There are clinical reports suggesting a better outcome of cardiac transplant in patients on statin therapy ( 1 ). Statin inhibits IFN-␥ -induced major histocompatibility complex class II (MHC II) expression but does not affect constitutive expression of MHC I and MHC II ( 2 ). Research, New Delhi, India and Network Project (Project NWP 0005 / BSC 0120 ; APC, antigen-presenting cell; CCM, cholesterol consensus motif; CRAC, cholesterol recognition/interaction amino-acid consensus; 3D, three-dimensional; m ␤ -CD, methyl ␤ -cyclodextrin; m ␤ -M ⌽ , methyl ␤ -cyclodextrin-treated macrophage; m ␤ -M ⌽ -CL, methyl ␤ -cyclodextrintreated macrophages treated with liposomal cholesterol; m ␤ -M ⌽ -CL-AN, methyl ␤ -cyclodextrin-treated macrophages treated with liposomal cholesterol analog; M ⌽ , macrophage; MHC I/II, major histocompatibility complex class I/II; mAb, monoclonal antibody; MFI, mean fl uorescence intensity; N-M ⌽ , normal macrophage; N-M ⌽ -CL, normal macrophages treated with liposomal cholesterol; PC, phosphatidylcholine; PEC, peritoneal exudate cell; TFE, trifl uoroethanol; TM, transmembrane; TM-MHC-II, transmembrane domain of major histocompatibility complex class II. This work was supported by the Council of Scientifi c and Industrial

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“…Unfortunately, the information content of these methods is often reduced by poor sensitivity (NMR), lack of sitespecific information (FT-IR), or the need to quench the exchange reaction or manipulate the solvent environment before the extent of exchange can be quantified [4,6]. HDX has also been studied by mass spectrometry (MS) techniques, with fruitful applications to soluble protein systems in the characterization of tertiary structure, folding, dynamics, and non-covalent interactions [8,9]. More recently, attempts have been made to use MS methods for monitoring HDX of membrane proteins in a range of lipid and detergent environments [6, 9 -12].…”

mentioning

confidence: 99%

Hydrogen/deuterium exchange of hydrophobic peptides in model membranes by electrospray ionization mass spectrometry

Hansen

Broadhurst

Skelton

et al. 2002

J. Am. Soc. Mass Spectrom.

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We demonstrate here that the hydrogen/deuterium solvent exchange (HDX) properties of the transmembrane fragment of the M2 protein of Influenza A (M2-TM) incorporated into lipid vesicles or detergent micelles can be studied with straightforward electrospray (ESI) and nanospray mass spectrometry (MS) configurations provided that key factors, including sample preparation techniques, are optimized. Small unilamellar vesicle preparations were obtained by solubilizing dimyristoyl phosphatidylcholine (DMPC) and the M2-TM peptide in aqueous solution with n-octyl-␤-D-glycopyranoside, followed by dialysis to remove the detergent. Electron microscopy experiments revealed that subsequent concentration by centrifugation introduced large multilamellar aggregates that were not compatible with ESI-MS. By contrast, a lyophilization-based concentration procedure, followed by thawing above the liquid crystal transition temperature of the lipid component, maintained the liposome size profile and yielded excellent ion fluxes in both ESI-MS and nano-ESI-MS. Using these methods the global HDX profile of M2-TM in aqueous DMPC vesicles was compared with that in methanol, demonstrating that several amide sites were protected from exchange by the lipid membrane. We also show that hydrophobic peptides can be detected by ESI-MS in the presence of a large molar excess of the detergent Triton X-100. The rate of HDX of M2-TM in Triton X-100 micelles was faster than that in DMPC vesicles but slower than when the peptide had been denatured in methanol. These results indicate that the accessibility of backbone amide sites to the solvent can be profoundly affected by membrane protein structure and dynamics, as well as the properties of model bilayer systems. (J Am Soc Mass Spectrom 2002, 13, 1376 -1387

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Solvent Effects on the Conformation of the Transmembrane Peptide Gramicidin A: Insights from Electrospray Ionization Mass Spectrometry

Cited by 27 publications

References 44 publications

The Preference of Tryptophan for Membrane Interfaces

The Preference of Tryptophan for Membrane Interfaces

Cholesterol lowering drug may influence cellular immune response by altering MHC II function

Hydrogen/deuterium exchange of hydrophobic peptides in model membranes by electrospray ionization mass spectrometry

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