1H-NMR study of GM2 ganglioside: evidence that an interresidue amide-carboxyl hydrogen bond contributes to stabilization of a preferred conformation |
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Authors: | Steven B Levery |
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Institution: | (1) The Biomembrane Institute, 201 Elliott Avenue West, 98119 Seattle, WA, USA |
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Abstract: | Several properties of the exchangeable amide protons of the ganglioside GM2 were studied in detail by1H-NMR spectroscopy in fully deuterated dimethylsulfoxide 2H6]DMSO/2% H2O, and compared with data obtained for the simpler constituent glycosphingolipids GA2 and GM3. In addition to chemical shifts,3
J
2,HN coupling constants, and temperature shift coefficients, the kinetics of NH/2H chemical exchange were examined by following the disappearance of the amide resonances in 2H6]DMSO/2%2H2O. The results included observation of an increase in half-life of theN-acetylgalactosamine acetamido HN by more than an order of magnitude in GM2 compared to GA2, attributable to the presence of the additionalN-acetylneuraminic acid residue. Additional one-dimensional dipolar cross relaxation experiments were also performed on nonexchangeable protons of GM2. The results of all of these experiments support a three-dimensional model for the terminal trisaccharide in which a hydrogen bond is formed between theN-acetylgalactosamine acetamido NH and theN-acetylneuraminic acid carboxyl group. The interaction is proposed to be of the -acceptor type, a possibility which has not yet been explored in the literature on carbohydrates. The proposed model is discussed in comparison with that of Sabesanet al. (1984,Can J Chem
62: 1034–45), and the models of GM1 proposed more recently by Acquottiet al. (1990,J Am Chem Soc
112:7772–8) and Scarsdaleet al. (1990,Biochemistry
29:9843–55). |
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Keywords: | GM2 ganglioside 1H-NMR three dimensional structure hydrogen bonding |
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