The unique three-dimensional arrangement of Macrophage Galactose Lectin enablesE. coliLipoPolySaccharides recognition through two distinct interfaces

Abstract

LipoPolySaccharides are a hallmark of Gram-negative bacteria and their presence at the cell surface is key for bacterial integrity. As surface exposed components, they are recognized by immunity C-type lectin receptors present on Antigen Presenting Cells. Human Macrophage Galactose Lectin bindsE. colisurface that presents a specific glycan motif. Nevertheless, this high affinity interaction occurs regardless of the integrity of its canonical calcium-dependent glycan binding site. Nuclear Magnetic Resonance of MGL carbohydrate recognition domain and complete extracellular domain revealed a new glycan binding site opposite to the canonical site. A model of trimeric Macrophage Galactose Lectin was determined based on a combination of Small Angle X-ray scattering and Alphafold. A disulphide bond positions the Carbohydrate Recognition Domain perpendicular to the coiled-coil domain. This unique configuration for a C-type lectin orients the six glycan sites of MGL in an ideal position to bind LipoPolySaccharides at the bacterial surface with high avidity.

Molecular recognition of Escherichia coli R1-type core lipooligosaccharide by DC-SIGN

“…To note, we have already observed such multivalent interaction between another C-type lectin, MGL, and R1-cells LOS. 43 …”

“…15 N-labelled DC-SIGN CRD was produced in M9 minimal medium with 15 NH 4 Cl as sole nitrogen source. 43 The product of dialysis after refolding was purified by an affinity chromatography on HisTrap HP column (GE Healthcare) equilibrated in buffer A, and eluted in the same buffer supplemented with 500 mM imidazole. This step was followed by a Toyopearl HW-50 S (Tosoh Bioscience) size exclusion chromatography equilibrated in buffer A.…”

Best Practices of Using AI-Based Models in Crystallography and Their Impact in Structural Biology

“…AF2 and RF should also prove very useful in combination with low-dimensionality structural methods, facilitating their interpretation, for example, with force spectroscopy, CD and SAXS − or FRET. Given the degeneracy associated with low-dimensionality methods, it is recommended to maximize the number of independent validations (see above).…”