5x4a

Publication Abstract from PubMed

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 non-motile (coccoid) symbiotic state. SLL-2 binds to the sugar chain of the molecule similar to Forssman antigen pentasaccharide (GalNAcalpha1-3GalNAcbeta1-3 Galalpha1-4 Galbeta1-4Glc) on the surface of microalgae with high affinity. Here we report the crystal structure of the complex between SLL-2 and Forssman antigen tetrasaccharide (GalNAcalpha1-3GalNAcbeta1-3 Galalpha1-4 Galbeta) at 3.4 A resolution. In an asymmetric unit of the crystal, there are two hexameric molecules with totally twelve sugar recognition sites. At the nine in twelve 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 alpha-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.

Crystal structure of octocoral lectin SLL-2 complexed with Forssman antigen tetrasaccharide.,Kita A, Jimbo M, Sakai R, Morimoto Y, Takeuchi R, Tanaka H, Takahashi T, Miki K Glycobiology. 2017 May 16. doi: 10.1093/glycob/cwx043. PMID:28510705^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.