Evidence that Caenorhabditis elegans 32-kDa beta-galactoside-binding protein is homologous to vertebrate beta-galactoside-binding lectins. cDNA cloning and deduced amino acid sequence.
We have cloned a full-length cDNA for a beta-galactoside-binding protein with a relative molecular mass of 32 kDa (32-kDa GBP), recently purified from a nematode, Caenorhabditis elegans (Hirabayashi, J., Satoh, M., Ohyama, Y., and Kasai, K. (1992) J. Biochem. 111, 553-555). The clone contained a single open reading frame encoding 279 amino acids, including the initiator methionine. Significant sequence homology to metal-independent beta-galactoside-binding lectins (25-30% identities), which had previously been found only in vertebrates, was observed. Moreover, the nematode 32-kDa GBP proved to have a unique polypeptide architecture; that is, it is composed of two tandemly repeated homologous domains, each consisting of about 140 amino acids. The internal homology was about 32%. Thus, this protein is constructed with a duplicated fundamental unit which is similar to the subunit of vertebrate 14-kDa lectins. In spite of the extreme phylogenic distance between nematodes and vertebrates (divergence greater than 6 x 10(8) years ago), both of the two repeated domains of the nematode 32-kDa GBP retained most of the amino acid residues conserved in vertebrate lectins. This means that members of the metal-independent animal lectin family are distributed much more widely than had been believed: from nematodes to vertebrates. The implication is that proteins belonging to this family have fundamental roles which are not restricted to vertebrates but are common to almost all animals.
Hirabayashi
J
J
Department of Biological Chemistry, Faculty of Pharmacological Sciences, Teikyo University, Kanagawa, Japan.
Satoh
M
M
Kasai
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002107:Caenorhabditis / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics*; D005697:Galactosides / Q000378:metabolism*; D037161:Galectins; D006388:Hemagglutinins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014714:Vertebrates / Q000235:genetics
D005697:Galactosides; D037161:Galectins; D006388:Hemagglutinins; D004247:DNA