Iris bulbs express type 1 and type 2 ribosome-inactivating proteins with unusual properties.
Two closely related lectins from bulbs of the Dutch iris (Iris hollandica var. Professor Blaauw) have been isolated and cloned. Both lectins, called Iris agglutinin b and Iris agglutinin r, possess N-glycosidase activity and share a high sequence similarity with previously described type 2 ribosome-inactivating proteins (RIP). However, these lectins show only 57% to 59% sequence identity to a previously characterized type 1 RIP from iris, called IRIP. The identification of the iris lectins as type 2 RIP provides unequivocal evidence for the simultaneous occurrence of type 1 and type 2 RIP in iris bulbs and allowed a detailed comparison of type 1 and type 2 RIP from a single plant, which provides further insight into the molecular evolution of RIP. Binding studies and docking experiments revealed that the lectins exhibit binding activity not only toward Gal/N-acetylgalactosamine, but also toward mannose, demonstrating for the first time that RIP-binding sites can accommodate mannose.
Hao
Q
Q
Laboratory for Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium.
Van Damme
E J
EJ
Hause
B
B
Barre
A
A
Chen
Y
Y
Rougé
P
P
Peumans
W J
WJ
D000595:Amino Acid Sequence; D031323:Iris Plant / Q000378:metabolism*; D037102:Lectins / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D011487:Protein Conformation; D012270:Ribosomes / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D037102:Lectins; D010940:Plant Proteins; D009699:N-Glycosyl Hydrolases