STRUCTURAL FEATURES OF MORACEAE
LECTINS
K. Sekar,a
J.V.Pratap,b A.A. Jeyaprakash,b A. Surolia,b and M. Vijayanb
aBioinformatics Centre and Supercomputer
Education and Research Centre; bMolecular Biophysics Unit, Indian Institute of
Science, Bangalore 560 012, India (sekar@physics.iisc.ernet.in)
Lectins are
carbohydrate-binding proteins, which mediate various biological processes. The b-prism fold was
first discovered in the galactose specific lectin jacalin from jackfruit
seeds. Structural studies on the
lectin, carried out in this laboratory, also established post translational
modification as a strategy for generating carbohydrate specificity. The homologous artocarpin, a second
lectin from jackfruit seeds, also assumes a b-prism fold. The absence of post translational modification and the
replacement of aromatic residues in the binding site, make it mannose
specific. Similar structures
determined in other laboratories include Maclura fomifera agglutinin (MPA), Helianthus tuberosus lectin (heltuba), domain II of d-endotoxin and the
vittelline membrane outer layer protein.
These structures among them, define the structural features of the b-prism fold as
indeed those of Moraceae
lectins. Among the proteins of the
structural family, the structures belonging to the lectin family (jacalin, MPA
and heltuba) have much more similarity amongst themselves than those belonging
to other types of proteins. In
addition, among the lectins, the similarity is higher with the Moraceae family (with jacalin and MPA), even when their
carbohydrate specificities are different. The details will be presented.