Porphyrin binding to jacalin is facilitated by the inherent plasticity of the carbohydrate-binding site: novel mode of lectin-ligand interaction.Goel, M., Anuradha, P., Kaur, K.J., Maiya, B.G., Swamy, M.J., Salunke, D.M.
(2004) Acta Crystallogr.,Sect.D 60: 281-288
- PubMed: 14747704
- DOI: 10.1107/S0907444903026684
- PubMed Abstract:
- Functional equality in the absence of structural similarity: an added dimension to molecular mimicry
Goel, M.,Jain, D.,Kaur, K.J.,Kenoth, R.,Maiya, B.G.,Swamy, M.J.,Salunke, D.M.
(2001) J.Biol.Chem. 276: 39277
The crystal structure of the complex of meso-tetrasulfonatophenylporphyrin (H(2)TPPS) with jack fruit (Artocarpus integriflora) agglutinin (jacalin) has been determined at 1.8 A resolution. A porphyrin pair is sandwiched between two symmetry-related ...
The crystal structure of the complex of meso-tetrasulfonatophenylporphyrin (H(2)TPPS) with jack fruit (Artocarpus integriflora) agglutinin (jacalin) has been determined at 1.8 A resolution. A porphyrin pair is sandwiched between two symmetry-related jacalin monomers in the crystal, leading to a cross-linking network of protein molecules. Apart from the stacking interactions, H(2)TPPS also forms hydrogen bonds, some involving water bridges, with jacalin at the carbohydrate-binding site. The residues that are involved in rendering galactopyranoside specificity to jacalin undergo conformational adjustments in order to accommodate the H(2)TPPS molecule. The water molecules at the carbohydrate-binding site of jacalin cement the jacalin-porphyrin interactions, optimizing their complementarity. Interactions of porphyrin with jacalin are relatively weak compared with those observed between galactopyranoside and jacalin, perhaps because the former largely involves water-mediated hydrogen bonds. While H(2)TPPS binds to jacalin at the carbohydrate-binding site as in the case of ConA, its mode of interaction with jacalin is very different. H(2)TPPS does not enter the carbohydrate-binding cavity of jacalin. Instead, it sits over the binding site. While the porphyrin binding is mediated by replicating the hydrogen-bonding network of mannopyranoside through the sulfonate atoms in the case of ConA, the plasticity associated with the carbohydrate-binding site accommodates the pluripotent porphyrin molecule in the case of jacalin through an entirely different set of interactions.
National Institute of Immunology, New Delhi 110067, India.