J Biol Chem, Vol. 274, Issue 53, 37673-37678, December 31, 1999

Purification, Characterization, and Amino Acid Sequence of an Embryonic Lectin in Perivitelline Fluid of the Horseshoe Crab^*

Taku Nagai, Shun-ichiro Kawabata^§¶, Fumio Shishikura, and Hiroaki Sugita^**

From the  Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, the ^§ Department of Biology, Kyushu University, Fukuoka 812-8581, the  Department of Biology, Nihon University School of Medicine, Tokyo 173-8610, and the ^** Institute of Biological Sciences, the University of Tsukuba, Ibaraki 305-8572, Japan

Hemagglutinating activity in perivitelline fluid of the horseshoe crab embryo dramatically increases during the third and fourth molt of the embryo. A 27-kDa lectin, which we named tachylectin-P (TL-P), was newly identified in perivitelline fluid of the horseshoe crab Tachypleus tridentatus. TL-P preferentially agglutinated human A-type erythrocytes, and the activity was inhibited by N-acetyl group-containing monosaccharides. The amino acid sequence analysis indicated that TL-P is almost structurally the same as a hemocyte-derived lectin with no hemagglutinating activity, tachylectin-1 (TL-1), and that 218 out of 221 amino acid residues in total were conserved between the two lectins. Despite the high sequence similarity, biological and biochemical characteristics of TL-P differed from those of TL-1: (i) unlike TL-1, TL-P agglutinates several animal-derived erythrocytes; (ii) unlike TL-1, TL-P has no significant affinity for bacterial lipopolysaccharides or antibacterial activity; (iii) Based on apparent molecular masses determined by gel filtration, TL-P forms a dimer in solution, while TL-1 is present as a monomer; (iv) and TL-P interacts with endogenous proteins of 13 and 14 kDa present in the perivitelline fluid; however, neither has any affinity for TL-1. We propose that TL-P may have an important role in completing embryonic development by interacting with endogenous glycoproteins or N-acetylhexosamines.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EMBL Data Bank with accession number(s) AB028144.