1RIT

Crystal structure of Peanut lectin in complex with meso-tetrasulphonatophenylporphyrin and lactose

Summary for 1RIT

• Entry DOI: 10.2210/pdb1rit/pdb
• Related: 1JN2 1PXD 1RIR
• Related PRD ID: PRD_900004
• Descriptor: Galactose-binding lectin, beta-D-galactopyranose-(1-4)-beta-D-glucopyranose, 5,10,15,20-TETRAKIS(4-SULPFONATOPHENYL)-21H,23H-PORPHINE, ... (6 entities in total)
• Functional Keywords: sugar binding protein
• Biological source: Arachis hypogaea (peanut)
• Total number of polymer chains: 4
• Total formula weight: 112229.70

Authors

Goel, M.,Kaur, K.J.,Maiya, B.G.,Swamy, M.J.,Salunke, D.M. (deposition date: 2003-11-17, release date: 2004-12-28, Last modification date: 2024-02-14)

Primary citation

Goel, M.,Damai, R.S.,Sethi, D.K.,Kaur, K.J.,Maiya, B.G.,Swamy, M.J.,Salunke, D.M.
Crystal structures of the PNA-porphyrin complex in the presence and absence of lactose: mapping the conformational changes on lactose binding, interacting surfaces, and supramolecular aggregations.
Biochemistry, 44:5588-5596, 2005

PubMed Abstract: The extraordinary recognition specificity of lectins for carbohydrate ligands appears to be violated as they also bind to porphyrins and other noncarbohydrate ligands. In this study, crystal structures of meso-tetrasulfonatophenylporphyrin (H(2)TPPS) bound to peanut agglutinin (PNA) in the presence and absence of lactose were determined. The binding of H(2)TPPS with PNA involved 11 molecules of H(2)TPPS in different supramolecular stacking arrangements associated with a tetramer of PNA in the crystals of the PNA-H(2)TPPS binary complex as well as the PNA-H(2)TPPS-lactose ternary complex. The ternary complex involved lactose binding only to two subunits of the PNA tetramer, which did not have porphyrin interacting in the vicinity of the carbohydrate-binding site. Comparison of the two structures highlighted the plasticity of the carbohydrate-binding site expressed in terms of the conformational change in lactose binding. The unusual quaternary structure of PNA, which results in exposed protein-protein interaction sites, might be responsible for the porphyrin binding. The association of porphyrin in diverse oligomeric stacking arrangements observed in the PNA-H(2)TPPS complex suggested the possibility of protein-porphyrin aggregation under abnormal physiological conditions. The structures described here provide a possible native conformation of the carbohydrate-binding site of PNA in the absence of the ligand, highlight mapping of the unsaturated binding surfaces of PNA using porphyrin interactions, indicate new leads toward possible application of this lectin in photodynamic therapy, and exhibit diverse modes of porphyrin-lectin interactions with implications to porphyria, a disease that results from abnormal accumulation of porphyrins.

PubMed: 15823017
DOI: 10.1021/bi047377s

Experimental method

X-RAY DIFFRACTION (2.85 Å)