Rahayu AP, Akhwan ZR, Karsono AH, Yoshida H, Utami RA, et al.
Biochemistry. Biokhimiia •
The effect of the C-terminal tail on the bioactivity of mannose-binding protein (Abmb) was investigated. Based on the earlier obtained crystal structure of Abmb, it was suggested that the additional C-terminal tail can modulate the binding of sugars to the protein. According to glycan microarray, Abmb can bind β-Gal sugars, which contradicted the results of SPR analysis showing that Abmb only interacts with α-Man and not with α-Gal. Here, we used MCF-7 and MDA-MB-231 breast cancer cells to demonstrate that the presence of the C-terminal tail decreased the anti-proliferative activity of Abmb. Pre-incubating Abmb with α-Gal did not eliminate the anti-proliferative activity, while pre-incubation with α-Man attenuated it. At the same time, preincubation with a mixture of α-Gal and α-Man strongly promoted the anti-proliferative activity of Abmb. analysis using molecular docking suggested the presence of a second functional sugar-binding site for Gal, which had not been identified previously. The study provides new insights into the structure of lectins and their interaction with sugars.
Fukunaga T, Tanaka N, Furumoto T, Nakakita S, Ohashi T, et al.
Glycobiology •
In the fission yeast Schizosaccharomyces pombe, α1,2- and α1,3-linked D-galactose (Gal) residues are transferred to N- and O-linked oligosaccharides of glycoproteins by galactosyltransferases. Although the galactomannans are important for cell-cell communication in S. pombe (e.g., in nonsexual aggregation), the mechanisms underlying galactosylation in cells remain unclear. Schizosaccharomyces pombe has 10 galactosyltransferase-related genes: seven belonging to glycosyltransferase (GT) family 34 and three belonging GT family 8. Disruption of all 10 α-galactosyltransferases (strain Δ10GalT) has been shown to result in a complete lack of α-Gal residues. Here, we have investigated the function and substrate specificities of galactosyltransferases in S pombe by using strains expressing single α-galactosyltransferases in the Δ10GalT background. High-performance liquid chromatography (HPLC) analysis of pyridylaminated O-linked oligosaccharides showed that two GT family 34 α1,2-galactosyltransferases (Gma12p and Gmh6p) and two GT family 8 α1,3-galactosyltransferases (Otg2p and Otg3p) are involved in galactosylation of O-linked oligosaccharide. Moreover, 1H-NMR of N-glycans revealed that three GT family 34 α1,2-galactosyltransferases (Gmh1p, Gmh2p and Gmh3p) are required for the galactosylation of N-linked oligosaccharides. Furthermore, HPLC and lectin-blot analysis revealed that Otg1p showed α1,3-galactosyltransferase activity under conditions of co-expression with Gmh6p, indicating that α-1,2-linked galactose is required for the galactosylation activity of Otg1p in S. pombe. In conclusion, eight galactosyltransferases have been shown to have activity in S. pombe with different substrate specificities. These findings will be useful for genetically tailoring the galactosylation of both N- and O-glycans in fission yeast.
