Cloning and characterization of a monocot mannose-binding lectin from Crocus vernus (family Iridaceae).
The molecular structure and carbohydrate-binding activity of the lectin from bulbs of spring crocus (Crocus vernus) has been determined unambiguously using a combination of protein analysis and cDNA cloning. Molecular cloning revealed that the lectin called C. vernus agglutinin (CVA) is encoded by a precursor consisting of two tandemly arrayed lectin domains with a reasonable sequence similarity to the monocot mannose-binding lectins. Post-translational cleavage of the precursor yields two equally sized polypeptides. Mature CVA consists of two pairs of polypeptides and hence is a heterotetrameric protein. Surface plasmon resonance studies of the interaction of the crocus lectin with high mannose-type glycans showed that the lectin interacts specifically with exposed alpha-1,3-dimannosyl motifs. Molecular modelling studies confirmed further the close relationships in overall fold and three-dimensional structure of the mannose-binding sites of the crocus lectin and other monocot mannose-binding lectins. However, docking experiments indicate that only one of the six putative mannose-binding sites of the CVA protomer is active. These results can explain the weak carbohydrate-binding activity and low specific agglutination activity of the lectin. As the cloning and characterization of the spring crocus lectin demonstrate that the monocot mannose-binding lectins occur also within the family Iridaceae a refined model of the molecular evolution of this lectin family is proposed.
Laboratory of Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Belgium; Institut de Pharmacologie et Biologie Structurale, Toulouse, France. Els.VanDamme@agr.kuleuven.ac.be
E J
EJ
Van Damme
C H
CH
Astoul
A
A
Barre
P
P
Rougé
W J
WJ
Peumans
D000373:Agglutinins; D000595:Amino Acid Sequence; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D037102:Lectins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D046911:Macromolecular Substances; D019684:Magnoliopsida / Q000737:chemistry / Q000235:genetics*; D008358:Mannose; D037241:Mannose-Binding Lectins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D037121:Plant Lectins; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D000373:Agglutinins; C414303:Crocus vernus agglutinin; D037102:Lectins; D046911:Macromolecular Substances; D037241:Mannose-Binding Lectins; D037121:Plant Lectins; D011994:Recombinant Proteins; D008358:Mannose