Structural characterisation of human galectin-4 N-terminal carbohydrate recognition domain in complex with glycerol, lactose, 3′-sulfo-lactose and 2′-fucosyllactose

Abstract

Galectin-4 is a tandem-repeat galectin with two distinct carbohydrate recognition domains (CRD). Galectin-4 is expressed mainly in the alimentary tract and is proposed to function as a lipid raft and adherens junction stabilizer by its glycan cross-linking capacity. Galectin-4 plays divergent roles in cancer and inflammatory conditions, either promoting or inhibiting each disease progression, depending on the specific pathological condition. The study of galectin-4’s ligand-binding profile may help decipher its roles under specific conditions. Here we present the X-ray structures of human galectin-4 N-terminal CRD (galectin-4N) bound to different saccharide ligands. Galectin-4’s overall fold and its core interactions to lactose are similar to other galectin CRDs. Galectin-4N recognises the sulfate cap of 3′-sulfated glycans by a weak interaction through Arg45 and two water-mediated hydrogen bonds via Trp84 and Asn49. When galectin-4N interacts with the H-antigen mimic, 2′-fucosyllactose, an interaction is formed between the ring oxygen of fucose and Arg45. The extended binding site of galectin-4N may not be well suited to the A/B-antigen determinants, α-GalNAc/α-Gal, specifically due to clashes with residue Phe47. Overall, galectin-4N favours sulfated glycans whilst galectin-4C prefers blood group determinants. However, the two CRDs of galectin-4 can, to a less extent, recognise each other’s ligands.

Structure-based rationale for differential recognition of lacto- and neolacto- series glycosphingolipids by the N-terminal domain of human galectin-8

“…Interestingly, the position of oxygen atom of glycerol in our structure along with the presence of a water molecule (mimicking O3 of glucose in the lactose-bound structure) matches exactly with the previously highlighted hotspots for ligand recognition from the galectin-3-glycerol structure (2NMO43). The conformation of glycerol in our structure is also identical to that observed in other high-resolution galectin-3 structure (3ZSK44) and also in the galectin-4 N structure (5DUU45). This indicates that the glycerol represents a moiety that exhibits key features desired for interaction by the galectins, though due to the smaller size, presence of only three hydroxyl groups and more importantly the lack of other key interactions (made by galactose) poses challenges in quantifying the glycerol binding affinity44.…”

Chicken GRIFIN: Structural characterization in crystals and in solution

“…S3). Interestingly, these sets include contacts to Asn48 and Arg50 as well as Trp66, albeit not with the same conformer, as is the case for the N-domains of Gal-4 and -8 [54,55]: Gal-4C, in contrast, appears to employ a transient contact to Trp256 for the slight affinity increase caused by the presence of the 3 0 -sulfate group [56]. When comparing in detail positions of amino acid of the ligandfree and -loaded subunits of the C-GRIFIN homodimer, one liganddependent event of reorganization was revealed (Fig.…”

An adipose tissue galectin controls endothelial cell function via preferential recognition of 3‐fucosylated glycans

“…44 Murine Gal-12N-CRD was constructed based on mGal-9N and mGal-4N crystal structures ( Figure 3A), and since no crystallized structure is available for the C-terminal domain of any murine tandem-repeat galectin, hGal-4C, hGal-8C, and hGal-9C were used as templates for mGal-12C-CRD ( Figure 3B). Furthermore, splitting the protein into the two CRDs allowed us to study each domain separately, as previously described for other tandem-repeat galectins.…”

“…Furthermore, splitting the protein into the two CRDs allowed us to study each domain separately, as previously described for other tandem-repeat galectins. 44 Murine Gal-12N-CRD was constructed based on mGal-9N and mGal-4N crystal structures ( Figure 3A), and since no crystallized structure is available for the C-terminal domain of any murine tandem-repeat galectin, hGal-4C, hGal-8C, and hGal-9C were used as templates for mGal-12C-CRD ( Figure 3B). Despite the low similarity sequence, all models successfully presented a GA341 score of 1.00, suggesting that they are reasonable models.…”