Caenorhabditis elegans galectins LEC-6 and LEC-1 recognize a chemically synthesized Galbeta1-4Fuc disaccharide unit which is present in Protostomia glycoconjugates.
Galbeta1-4GlcNAc is thought to be a common disaccharide unit preferentially recognized by vertebrate galectins. Eight-amino-acid residues conserved in proteins belonging to the galectin family have been suggested to be responsible for recognition. Meanwhile, we isolated and analyzed endogenous N-glycans of Caenorhabditis elegans that were captured by a C. elegans galectin LEC-6 and demonstrated that the unit of recognition for LEC-6 is a Gal-Fuc disaccharide, though the linkage between these residues was not confirmed. In the present study, we chemically synthesized Galbeta1-4Fuc and Galbeta1-3Fuc labeled with 2-aminopyridine (PA) and demonstrated that LEC-6 interacts with PA-Galbeta1-4Fuc more strongly than PA-Galbeta1-3Fuc by frontal affinity chromatography (FAC). Galbeta1-4Fuc also inhibited hemagglutination caused by LEC-6 more strongly than Galbeta1-3Fuc. FAC analysis using LEC-6 point mutants revealed that some of the conserved amino acid residues which have proven to be important for the recognition of Galbeta1-4GlcNAc are not necessary for the binding to Galbeta1-4Fuc. Another major C. elegans galectin, LEC-1, also showed preferential binding to Galbeta1-4Fuc. These results suggest that Galbeta1-4Fuc is the endogenous unit structure recognized by C. elegans galectins, which implies that C. elegans glycans and galectins may have co-evolved through an alteration in the structures of C. elegans glycans and a subsequent conversion in the sugar-binding mechanism of galectins. Furthermore, since glycans containing the Galbeta1-4Fuc disaccharide unit have been found in organisms belonging to Protostomia, this unit might be a common glyco-epitope recognized by galectins in these organisms.
Takeuchi
Tomoharu
T
Department of Biological Chemistry, School of Pharmaceutical Sciences, Teikyo University, 1091-1 Suarashi, Sagamiko, Sagamihara, Kanagawa 229-0195, Japan. t-take@pharm.teikyo-u.ac.jp
Nishiyama
Kazusa
K
Sugiura
Ken-Ichi
K
Takahashi
Miki
M
Yamada
Atsushi
A
Kobayashi
Susumu
S
Takahashi
Hideyo
H
Natsugari
Hideaki
H
Kasai
Ken-ichi
K
D000595:Amino Acid Sequence; D000818:Animals; D000947:Antigens, Helminth / Q000737:chemistry / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000737:chemistry / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism*; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D037161:Galectins / Q000737:chemistry / Q000378:metabolism*; D006001:Glycoconjugates / Q000737:chemistry* / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D013379:Substrate Specificity
D000947:Antigens, Helminth; D029742:Caenorhabditis elegans Proteins; D004187:Disaccharides; D037161:Galectins; D006001:Glycoconjugates; C534045:LEC-6 protein, C elegans; C525184:Lec-1 protein, C elegans; C547518:galactopyranosyl-1-4-fucose