NMR and Molecular Modeling Studies of the Interaction between Wheat Germ Agglutinin and the -D

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• 作者：Kristina Lycknert ; Malin Edblad ; Anne Imberty ; and G&ouml ; ran Widmalm
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：August 3, 2004
• 年：2004
• 卷：43
• 期：30
• 页码：9647 - 9654
• 全文大小：374K
• 年卷期：v.43,no.30(August 3, 2004)
• ISSN：1520-4995

文摘

The SRC="/images/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-D-GlcpNAc-(1s/entities/rarr.gif">6)-s/gifchars/alpha.gif" BORDER=0>-D-Manp disaccharide is a constituent of highly branched cell-surface glycoconjugates that are malignancy markers. The conformational preference of the disaccharides/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-D-GlcpNAc-(1s/entities/rarr.gif">6)-s/gifchars/alpha.gif" BORDER=0>-D-Manp-OMe in solution has been studied by molecular modeling and NMRspectroscopy including 1D ¹H,¹H T-ROESY experiments and analysis of ³J_H,H of the hydroxymethyl groupbeing part of the glycosidic linkage of the disaccharide, which revealed the relative populations of the s/gifchars/omega.gif" BORDER=0 >torsion angle as gt = 0.60, gg = 0.35, and tg = 0.05. Good agreement was obtained between the effectiveproton-proton distances from the experiment and those obtained by molecular modeling when the flexibilityat the s/gifchars/omega.gif" BORDER=0 > torsion angle was taken into account. Molecular modeling of the disaccharide in the binding sitesof the lectin wheat germ agglutinin indicates that several conformations could be adopted in the boundstate. ¹H NMR and transfer NOESY experiments confirmed that binding took place, and trans-glycosidicproton-proton interactions indicated that a conformational preference was present in the bound state, asobserved by the relative change of the NOEs from H1' to H6_pro-R and H6_pro-S. STD NMR experimentsshowed that binding occurred in the region of the N-acetyl group of the terminal sugar residue. In addition,the O-methyl group received saturation transfer because of the proximity to the protein. ¹H,¹H NOEsindicated that the two methyl groups were close in space, as observed in only one of the predicted boundconformations. Experimental and theoretical data therefore agree that one conformation with a gtconformation of the hydroxymethyl group and a negative sign for the s/gifchars/psi.gif" BORDER=0 > torsion angle is indeed selectedby the lectin upon binding.