Porphyrin binding to jacalin is facilitated by the inherent plasticity of the carbohydrate-binding site: novel mode of lectin–ligand interaction

Abstract

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.

Interaction of Wheat Germ Agglutinin with Porphyrin Compounds—Potential Anticancer Agents

“…An alternative approach has been studied and applied using some plant lectins, such as snake gourd Trichosanthes anguina, legume Concanavalin A, and pea lectin, that have been found to bind porphyrins and may have potential application in targeted PDT (3,12,13,14,17,20,22). Our data are the first to demonstrate the porphyrin binding capacity of WGA lectin.…”

“…Therefore, in order to improve the selective recognition of tumour cells by porphyrins, several plant lectins have been tested as drug delivery agents for these sensitizers (11). Previous spectroscopic and crystallographic studies have shown that some plant lectins (snake gourd Trichosantes anguina seed lectin, concanavalin A, peanut lectin, jacalin) can bind porphyrins (3,12,13,14,17,22,20).…”

Porphyrins as the Inhibitors of Viral Infection in Plant Tissue Culture

“…Â прèроді порфірèíè â осíоâíоìу зíàходÿтьсÿ â коìплексі з білкàìè. Тàк, íàпрèклàд, прè обробöі лектèíу Artocarpus integriflora ìезо-тетрà (сульфо-íàтофеíіл) порфірèíоì (H2TPPS) âідбуâàєтьсÿ з'єдíàííÿ ìолекул порфірèíу з білкоâèìè ìолекулàìè з утâореííÿì «білкоâої сіткè» [6]. Порфірèíè здàтíі прèєдíуâàтèсь до ДНК àбо РНК тà âèклèкàтè їх дегрàдà-öію [4,10].…”

Binding of Antitumor Compounds to Wheat Protein

“…interestingly, some lectins such as: snake gourd Trichosantes anguina seed lectin, concanavalin A, peanut lectin and jacalin bind photosensitizers (4,9,10,11,13,17,18).…”