Sialic acid-binding dwarf elder four-chain lectin displays nucleic acid N-glycosidase activity.
Sialic acid-binding dwarf elder agglutinin (SEA) present only in rhizomes of the medicinal plant Sambucus ebulus L., was found to be a tetrameric glycoprotein consisting of two covalently-associated dimers of an enzymic A chain with rRNA N-glycosidase activity (EC 3.2.2.22) linked to a B chain with agglutinin properties. The lectin inhibited protein synthesis by a cell-free system and depurinated ribosomes. Cloning of the corresponding gene and molecular modeling of the deduced amino acid sequence demonstrated that SEA has a three-dimensional structure which resembles that reported for other two tetrameric type 2 RIPs from Sambucus (SNAI and SSA). The lectin agglutinated red blood cells and displayed sugar affinity for sialic acid residues apart from d-galactose, binding to the mucin-producing gut goblet cells. Since sialic acid is present in animal cells, especially in epithelial lining gut cells, but not in plants, SEA could play a role in the defense against insect attack. The nucleotide sequence reported in this paper has been submitted to the GenBank nucleotide database under accession number AM981401.
Iglesias
Rosario
R
Departamento de Bioquímica y Biología Molecular, Universidad de Valladolid, Spain.
Citores
Lucía
L
Ferreras
J Miguel
JM
Pérez
Yolanda
Y
Jiménez
Pilar
P
Gayoso
Manuel J
MJ
Olsnes
Sjur
S
Tamburino
Rachele
R
Di Maro
Antimo
A
Parente
Augusto
A
Girbés
Tomás
T
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D055598:Chemical Phenomena; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006384:Hemagglutination / Q000187:drug effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D009696:Nucleic Acids / Q000378:metabolism*; D010802:Phylogeny; D037121:Plant Lectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D020836:Protein Structure, Quaternary; D027343:Rhizome; D054790:Ribosome Inactivating Proteins, Type 2 / Q000737:chemistry / Q000378:metabolism; D027923:Sambucus
D009696:Nucleic Acids; D037121:Plant Lectins; D054790:Ribosome Inactivating Proteins, Type 2; D006026:Glycoside Hydrolases; D019158:N-Acetylneuraminic Acid