Primary structure of hemolytic lectin CEL-III from marine invertebrate Cucumaria echinata and its cDNA: structural similarity to the B-chain from plant lectin, ricin.
CEL-III, a galactose/N-acetylgalactosamine (Gal/GalNAc) specific lectin purified from a marine invertebrate Cucumaria echinata has a strong hemolytic activity especially toward human and rabbit erythrocytes. We determined the primary structure of the CEL-III by examining the amino acid sequences of the protein and the nucleotide sequence of the cDNA. The cDNA encoding CEL-III has 1823 nucleotides and an open reading frame of 1296 nucleotides. CEL-III is composed of 432 amino acid residues with a M(r) of 47¿ omitted¿457 and has six internal tandem repeats, each with of 40-50 amino acids, comprising the N-terminal two-thirds of the molecule. Similar repeats are found in the B-chains of cytotoxic plant lectins, such as ricin and abrin, where six repetitive sequences extend throughout the molecules. A hydropathy plot predicts hydrophobic segments in the C-terminal region of CEL-III. These findings suggest that the N-terminal region of CEL-III plays an important role in binding to carbohydrate receptors on the target cell membranes, an event which triggers an intermolecular hydrophobic interaction of the C-terminal region, the result being oligomerization of CEL-III to lead to pore-formation in erythrocyte membrane.
Nakano
M
M
Laboratory of Biochemistry, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, Japan.
Tabata
S
S
Sugihara
K
K
Kouzuma
Y
Y
Kimura
M
M
Yamasaki
N
N
D000036:Abrin / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D037102:Lectins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D012276:Ricin / Q000737:chemistry
C402644:CEL-III lectin, Cucumaria echinata; D018076:DNA, Complementary; D037102:Lectins; D000036:Abrin; D012276:Ricin