5X4A

SLL-2-Forssman antigen tetrasaccharides complex

Summary for 5X4A

• Entry DOI: 10.2210/pdb5x4a/pdb
• Descriptor: Galactose-binding lectin, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, 2-acetamido-2-deoxy-alpha-D-galactopyranose-(1-3)-2-acetamido-2-deoxy-beta-D-galactopyranose-(1-3)-alpha-D-galactopyranose-(1-4)-beta-D-galactopyranose, ... (5 entities in total)
• Functional Keywords: coral lectin, sll-2, symbiosis, forssman antigen tetrasaccharides, sugar binding protein
• Biological source: Sinularia lochmodes
• Total number of polymer chains: 12
• Total formula weight: 142311.80

Authors

Kita, A.,Miki, K. (deposition date: 2017-02-11, release date: 2017-09-20, Last modification date: 2024-11-20)

Primary citation

Kita, A.,Jimbo, M.,Sakai, R.,Morimoto, Y.,Takeuchi, R.,Tanaka, H.,Takahashi, T.,Miki, K.
Crystal structure of octocoral lectin SLL-2 complexed with Forssman antigen tetrasaccharide.
Glycobiology, 2017

PubMed Abstract: A symbiosis-related lectin, SLL-2, from the octocoral Sinularia lochmodes, distributes densely on the cell surface of microalgae, Symbiodinium sp., an endosymbiotic dinoflagellate of the coral, and is also shown to be a chemical cue that transforms dinoflagellates into a nonmotile (coccoid) symbiotic state. SLL-2 binds to the sugar chain of the molecule similar to Forssman antigen pentasaccharide (GalNAcα1-3GalNAcβ1-3 Galα1-4 Galβ1-4Glc) on the surface of microalgae with high affinity. Here we report the crystal structure of the complex between SLL-2 and Forssman antigen tetrasaccharide (GalNAcα1-3GalNAcβ1-3 Galα1-4 Galβ) at 3.4 Å resolution. In an asymmetric unit of the crystal, there are two hexameric molecules with totally 12 sugar recognition sites. At 9 in 12 sites, the first and second saccharides of the Forssman antigen tetrasaccharide bind directly to galactopyranoside binding site of SLL-2, whereas the third and fourth saccharides have no interaction with the SLL-2 hexameric molecule that binds the first saccharide. The sugar chain bends at α-1,4-glycosidic linkage between the third and fourth saccharides toward the position that we defined as a pyranoside binding site in the crystal structure of the complex between SLL-2 and GalNAc. The structure allowed us to suggest a possible binding mode of the Forssman antigen pentasaccharide to SLL-2. These observations support our hypothesis that the binding of SLL-2 to the cell surface sugars of zooxanthella in a unique manner might trigger some physiological changes of the cell to adapt symbiosis with the host coral.

PubMed: 28510705
DOI: 10.1093/glycob/cwx043

Experimental method

X-RAY DIFFRACTION (3.4 Å)