Conformational Investigation of a Cyclic Enterobacterial Common Antigen Employing NMR Spectroscopy and Molecular Dynamics Simulations

• Published in: Biochemistry (Easton) Vol. 40; no. 12; pp. 3623 - 3628
• Main Authors: Staaf, Mikael, Höög, Christer, Stevensson, Baltzar, Maliniak, Arnold, Widmalm, Göran
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27-03-2001
• Subjects: Antigens, Bacterial - chemistry; Carbohydrate Conformation; Carbohydrate Sequence; Computer Simulation; Glucans - chemistry; Models, Chemical; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular - methods; Plesiomonas - chemistry; Plesiomonas - immunology; Polysaccharides - chemistry; Protons; Solutions; Thermodynamics; Trisaccharides - chemistry
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi002282l

The three-dimensional structure of a cyclic enterobacterial common antigen (ECA) having four trisaccharide repeating units has been investigated by NMR spectroscopy and molecular dynamics simulations. Three different NMR parameters were determined:  (a) 1H,1H cross-relaxation rates from NOE experiments were used for determination of proton−proton distances; (b) trans-glycosidic 3 J C,H scalar coupling constants analyzed via a Karplus-type relationship provided information on torsion angles; and (c) 1H,13C one-bond dipolar couplings obtained in a dilute liquid-crystalline medium were interpreted in terms of the orientational order and molecular conformations. The molecular dynamics simulations of the dodecasaccharide were performed with explicit water and counterions, which are important factors that strongly influence molecular conformation. Subsequently, the results from computer simulation were used to generate a three-dimensional structure of the cyclic ECA which is consistent with the experimental NMR parameters.