title: Complement Factor H and Simian Virus 40 bind the GM1 ganglioside in distinct conformations.
abstract: Mammalian cell surfaces are decorated with a variety of glycan chains that orchestrate development and defense and are exploited by pathogens for cellular attachment and entry. While glycosidic linkages are, in principle, flexible, the conformational space that a given glycan can sample is subject to spatial and electrostatic restrictions imposed by its overall chemical structure. Here, we show how the glycan moiety of the GM1 ganglioside, a branched, monosialylated pentasaccharide that serves as a ligand for various proteins, undergoes differential conformational selection in its interactions with different lectins. Using STD NMR and X-ray crystallography, we found that the innate immune regulator complement Factor H (FH) binds a previously not reported GM1 conformation that is not compatible with the GM1-binding sites of other structurally characterized GM1-binding lectins such as the Simian Virus 40 (SV40) capsid. Molecular dynamics simulations of the free glycan in explicit solvent on the 10 μs timescale reveal that the FH-bound conformation nevertheless corresponds to a minimum in the Gibbs free energy plot. In contrast to the GM1 conformation recognized by SV40, the FH-bound GM1 conformation is associated with poor NOE restraints, explaining how it escaped(1)H-(1)H NOE-restrained modeling in the past and highlighting the necessity for ensemble representations of glycan structures.
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen 72076, Germany baerbel.blaum@uni-tuebingen.de.
authors.forename: Bärbel S
authors.initials: BS
authors.lastname: Blaum
authors.affiliation: Biognos AB, Generatorsgatan 1, Gothenburg 41705, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Frank
authors.affiliation: San Diego Supercomputer Center and Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Ross C
authors.initials: RC
authors.lastname: Walker
authors.affiliation: Max-Planck-Institute of Colloids and Interfaces, Potsdam 14476, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Neu
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen 72076, Germany Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37212, USA.
authors.forename: Thilo
authors.initials: T
authors.lastname: Stehle
mesh_terms: D002213:Capsid / Q000737:chemistry* / Q000378:metabolism; D017242:Complement Factor H / Q000737:chemistry* / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D056004:Molecular Dynamics Simulation; D013539:Simian virus 40 / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005677:G(M1) Ganglioside; C029624:ganglioside M1b; D017242:Complement Factor H
keywords: carbohydrate; crystallography; innate immunity; molecular dynamics; saturation transfer difference NMR