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Exploration of the molecular recognition and dynamic properties of WaaG glycosyltransferase
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-30118OAI: oai:DiVA.org:su-30118DiVA: diva2:241528
Available from: 2009-10-04 Created: 2009-10-04 Last updated: 2011-04-19Bibliographically approved
In thesis
1. Structure, dynamics and interactions of biomolecules: Investigations by NMR spectroscopy and computational methods
Open this publication in new window or tab >>Structure, dynamics and interactions of biomolecules: Investigations by NMR spectroscopy and computational methods
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, the structure, dynamics and interactions of proteins and carbohydrates are investigated using mainly NMR spectroscopy and computer simulations.

Oligosaccharides representing a Salmonella O-antigen have been synthesized and their dynamic behavior and interaction with the bacteriophage P22 tail-spike protein have been studied by NMR spectroscopy, MD and docking simulations. A binding mechanism between the protein and the O-antigen has been proposed.

Transient hydrogen bonds have been defined and examined in an E. coli polysaccharide and in a pentasaccharide representing the repeating unit, using MD simulation and NMR spectroscopy.

Conformational dynamics of a trisaccharide representing the repeating unit of an A. salmonicida O-antigen have been investigated by MD simulations. The simulation together with relaxation matrix calculations reveals a conformational exchange on a ns timescale and explains an unusual NOE.

A fragment-based screening for inhibitors of the glycosyltransferase GTB acceptor site has been performed using NMR spectroscopy and SPR. IC50 values of the binding fragments are reported. Complex structures of the fragments and GTB have been proposed using docking simulations.

A fragment-based screening for inhibitors of the WaaG glycosyltransferase donor site has been performed using NMR spectroscopy and three compounds were selected. Structures of the WaaG-fragment complexes have been suggested from docking simulations. Binding of natural substrates and activity has also been investigated by NMR spectroscopy. MD simulations have been carried out on WaaG with and without bound donor substrate. The simulation revealed a conformational change upon substrate binding.

Interactions between HEWL and carbohydrate ligands have been investigated, using a combination of weak affinity chromatography, NMR spectroscopy and computer simulations. KDs of the ligands have been presented as well as the solution structures of two HEWL-disaccharide complexes.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2009. 82 p.
Keyword
NMR spectroscopy, MD simulation, carbohydrate synthesis, protein-ligand interaction, glycosyltransferase
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-30120 (URN)978-91-7155-953-1 (ISBN)
Public defence
2009-11-13, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Submitted. Paper 5: In progress. Paper 6: In progress. Paper 7: Manuscript.Available from: 2009-10-22 Created: 2009-10-04 Last updated: 2011-11-23Bibliographically approved
2. Computer-Assisted Carbohydrate Structural Studies and Drug Discovery
Open this publication in new window or tab >>Computer-Assisted Carbohydrate Structural Studies and Drug Discovery
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbohydrates are abundant in nature and have functions ranging from energy storage to acting as structural components. Analysis of carbohydrate structures is important and can be used for, for instance, clinical diagnosis of diseases as well as in bacterial studies. The complexity of glycans makes it difficult to determine their structures. NMR spectroscopy is an advanced method that can be used to examine carbohydrates at the atomic level, but full assignments of the signals require much work. Reliable automation of this process would be of great help. Herein studies of Escherichia coli O-antigen polysaccharides are presented, both a structure determination by NMR and also research on glycosyltransferases which assemble the polysaccharides. The computer program CASPER has been improved to assist in carbohydrate studies and in the long run make it possible to automatically determine structures based only on NMR data.

Detailed computer studies of glycans can shed light on their interactions with proteins and help find inhibitors to prevent unwanted binding. The WaaG glycosyltransferase is important for the formation of E. coli lipopolysaccharides. Molecular docking analyses of structures confirmed to bind this enzyme have provided information on how inhibitors could be composed. Noroviruses cause gastroenteritis, such as the winter vomiting disease, after binding human histo-blood group antigens. In one of the projects, fragment-based docking, followed by molecular dynamics simulations and binding free energy calculations, was used to find competitive binders to the P domain of the capsid of the norovirus VA387. These novel structures have high affinity and are a very good starting point for developing drugs against noroviruses. The protein targets in these two projects are carbohydrate binding, but the techniques are general and can be applied to other research projects.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. 78 p.
Keyword
Carbohydrates, molecular docking, molecular dynamics simulation, fragment-based virtual screening, NMR spectroscopy, computer-aided drug design, computer-aided structure elucidation, glycosyltransferases, Escherichia coli
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-56411 (URN)978-91-7447-245-5 (ISBN)
Public defence
2011-05-25, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript. Paper 6. Manuscript.Available from: 2011-05-03 Created: 2011-04-15 Last updated: 2012-07-03Bibliographically approved

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