Human intelectin is a novel soluble lectin that recognizes galactofuranosein carbohydrate chains of bacterial cell wall

Galactofuranosyl residues are present in various microorganisms but not in mammals, In this study, we identified a human lectin binding to galactofura nosyl residues and named this protein human intelectin (hIntL). The mature hIntL was a secretory glycoprotein consisting of 295 amino acids and N-link ed oligosaccharides, and its basic structural unit was a 120-kDa homotrimer in which 40-kDa polypeptides mere bridged by disulfide bonds. The hIntL ge ne was spilt into 8 exons on chromosome 1q21.3, and hIntL mRNA was expresse d in the heart, small intestine, colon, and thymus, hIntL showed high level s of homology with mouse intelectin, Xenopus laevis cortical granule lectin /oocyte lectin, lamprey serum lectin, and ascidian galactose-specific lecti n, These homologues commonly contained no carbohydrate recognition domain, which is a characteristic of C-type lectins, although some of them have bee n reported as Ca2+-dependent lectins. Recombinant hIntL revealed affinities to D-pentoses and a D-galactofuranosyl residue in the presence of Ca2+, an d recognized the bacterial arabinogalactan of Nocardia containing D-galacto furanosyl residues. These results suggested that hIntL is a new type lectin recognizing galactofuranose, and that hIntL plays a role in the recognitio n of bacteria-specific components in the host.