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Effect of the Substituents of the Neighboring Ring in the Conformational Equilibrium of Iduronate in Heparin-like Trisaccharides

Authors

  • Juan Carlos Muñoz-García,

    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
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    • These authors have contributed equally to this work

  • Dr. Javier López-Prados,

    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
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    • These authors have contributed equally to this work

  • Dr. Jesús Angulo,

    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
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  • Irene Díaz-Contreras,

    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
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  • Dr. Niels Reichardt,

    1. Laboratory of Glyconanotechnology, CIC-BiomaGUNE, CIBER-BBN, Paseo Miramón 182, Parque Tecnológico, 20009 San Sebastián (Spain)
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  • Dr. José L. de Paz,

    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
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  • Prof. Manuel Martín-Lomas,

    1. Laboratory of Glyconanotechnology, CIC-BiomaGUNE, CIBER-BBN, Paseo Miramón 182, Parque Tecnológico, 20009 San Sebastián (Spain)
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  • Dr. Pedro M. Nieto

    Corresponding author
    1. Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65
    • Glycosystems Laboratory, Instituto de Investigaciones Quimicas, CSIC - US, Americo Vespucio, 49, 41092 Sevilla (Spain), Fax: (+34) 954-46-01-65===

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Abstract

Based on the structure of the regular heparin, we have prepared a smart library of heparin-like trisaccharides by incorporating some sulfate groups in the sequence α-D-GlcNS- (1-4)-α-L-Ido2S-(1-4)-α-D-GlcN. According to the 3D structure of heparin, which features one helix turn every four residues, this fragment corresponds to the minimum binding motif. We have performed a complete NMR study and found that the trisaccharides have a similar 3D structure to regular heparin itself, but their spectral properties are such that allow to extract very detailed information about distances and coupling constants as they are isotropic molecules. The characteristic conformational equilibrium of the central iduronate ring has been analyzed combining NMR and molecular dynamics and the populations of the conformers of the central iduronate ring have been calculated. We have found that in those compounds lacking the sulfate group at position 6 of the reducing end glucosamine, the population of 2S0 of the central iduronate residue is sensitive to the temperature decreasing to 19 % at 278 K. On the contrary, the trisaccharides with 6-O-sulfate in the reducing end glucosamine keep the level of population constant with temperature circa 40 % of 2S0 similar to that observed at room temperature. Another structural feature that has been revealed through this analysis is the larger flexibility of the L-IdoAS- D-GlcN glycosidic linkage, compared with the D-GlcNS-L-IdoA. We propose that this is the point where the heparin chain is bended to form structures far from the regular helix known as kink that have been proposed to play an important role in the specificity of the heparin–protein interaction.

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