2005 年 28 巻 5 号 p. 791-796
Two C-type lectins (OLLafs and OLLafl) were isolated from Osmerus (Spirinchus) lanceolatus eggs using asialofetuin-Sepharose column. OLLafs and OLLafl were eluted with 0.2 M sucrose and 0.2 M lactose from the same column, respectively. OLLafl has been estimated to be a heterodimeric protein composed of H- and L-subunit and involved C-type lectin like domain (CTLD). In this study we revealed that OLLafs was a homodimeric protein composed of L-subunit of OLLafl. Although adding EDTA diminished the hemagglutinating activity of OLLafs, the activity of OLLafl was not influenced. Recombinant lectins (rOLLafl-H and -L) and mutant lectins replaced Cys123, 131 and 136 with Ala (mOLLafl-L123, 131 and 136) were established. The activity of mOLLafl-L136 was comparable to rOLLafl-L, and rOLLafl-H was 15 times lower than rOLLafl-L. On the other hand, the activity of mOLLafl-L123 and mOLLafl-L131 were lower than that of rOLLafl-H. Therefore, Cys136 may not participate in hemagglutinating activity of rOLLafl-L. In contrast, Cys123 and Cys131 may partially contribute this activity. Although hemagglutination inhibition profiles of rOLLafl-L, rOLLafl-H and mOLLafl-L136 were similar, m-OLLafl-L131-induced hemagglutination was not inhibited by any sugars tested even at a concentration of 150 mM. Then, Cys131 may directly contribute to the sugar-binding capacity of OLLafl. Affinities of mOLLafl-L123 for these sugars were lower than the others. These results suggest that Cys136 might contribute to the intermolecular disulfide bond in the rOLLafl-L dimer, and that the intramolecular disulfide bond concerning Cys131 might important for lectin activity.