title: Conformational changes in mannan-binding lectin bound to ligand surfaces.
abstract: The binding of soluble proteins to target surfaces is vital in triggering the immune response. However, structural insight into such processes is still lacking. Mannan-binding lectin (MBL) is a classic example of a pattern recognition molecule with important roles in innate immunity against microbial infections. By small angle x-ray scattering analysis we show that the large MBL complex in solution is folded into a ramified structure with a striking rotational symmetry and a structure permissive of elongation by unbending. Nevertheless, the structure in solution is found to be very stable. However, when the MBL molecule interacts with surface-immobilized ligands, the stable MBL structure is broken into a stretched state with separation of the ligand-binding domains as shown by high resolution atomic force microscopy. These studies provide a snapshot of the single molecule mechanics of MBL and the first direct evidence that the transition from the soluble state to surface-bound protein involves large conformational changes in the quaternary structure, thus highlighting the role of surface topography in immune recognition.
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Physiucs and Astronomy, University of Aarhus, Aarhus C, Denmark.
authors.forename: Mingdong
authors.initials: M
authors.lastname: Dong
authors.forename: Sailong
authors.initials: S
authors.lastname: Xu
authors.forename: Cristiano L P
authors.initials: CL
authors.lastname: Oliveira
authors.forename: Jan S
authors.initials: JS
authors.lastname: Pedersen
authors.forename: Steffen
authors.initials: S
authors.lastname: Thiel
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher
authors.forename: Thomas
authors.initials: T
authors.lastname: Vorup-Jensen
mesh_terms: D006801:Humans; D007113:Immunity, Innate / Q000502:physiology; D008024:Ligands; D037601:Mannose-Binding Lectin / Q000737:chemistry* / Q000276:immunology; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D037601:Mannose-Binding Lectin