Sialylated oligosaccharide-specific plant lectin from Japanese elderberry (Sambucus sieboldiana) bark tissue has a homologous structure to type II ribosome-inactivating proteins, ricin and abrin. cDNA cloning and molecular modeling study.
Bark lectins from the elderberry species belonging to the genus Sambucus have a unique carbohydrate binding specificity for sialylated glycoconjugates containing NeuAc(alpha 2-6)Gal/GalNAc sequence. To elucidate the structure of the elderberry lectin, a cDNA library was constructed from the mRNA isolated from the bark tissue of Japanese elderberry (Sambucus sieboldiana) with lambda gt11 phage and screened with anti-S. sieboldiana agglutinin (SSA) antibody. The nucleotide sequence of a cDNA clone encoding full-length SSA (LecSSA1) showed the presence of an open reading frame with 1902 base pairs, which corresponded to 570 amino acid residues. This open reading frame encoded a signal peptide and a linker region (19 amino acid residues) between the two subunits of SSA, the hydrophobic (A-chain) and hydrophilic (B-chain) subunits. This indicates that SSA is synthesized as a preproprotein and post-translationally cleaved into two mature subunits. Homology searching as well as molecular modeling studies unexpectedly revealed that each subunit of SSA has a highly homologous structure to the galactose-specific lectin subunit and ribosome-inactivating subunit of plant toxic proteins such as ricin and abrin, indicating a close evolutionary relationship between these carbohydrate-binding proteins.
Kaku
H
H
Department of Cell Biology, National Institute of Agrobiological Resources, Tsukuba, Japan.
Tanaka
Y
Y
Tazaki
K
K
Minami
E
E
Mizuno
H
H
Shibuya
N
N
D000036:Abrin / Q000737:chemistry* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003196:Computer Graphics; D037102:Lectins / Q000096:biosynthesis / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010446:Peptide Fragments / Q000737:chemistry; D037121:Plant Lectins; D010944:Plants / Q000235:genetics; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000737:chemistry; D017433:Protein Structure, Secondary; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012156:Reticulocytes / Q000378:metabolism; D054788:Ribosome Inactivating Proteins; D012270:Ribosomes / Q000187:drug effects; D012276:Ricin / Q000737:chemistry* / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid
D037102:Lectins; D010446:Peptide Fragments; D037121:Plant Lectins; D011498:Protein Precursors; D011994:Recombinant Proteins; C050600:Sambucus nigra lectins; D000036:Abrin; D012276:Ricin; D054788:Ribosome Inactivating Proteins