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.