Affinity of a galactose‐specific legume lectin from Dolichos lablab to adenine revealed by X‐ray cystallography

Abstract

Crystal structure analysis of a galactose-specific lectin from a leguminous food crop Dolichos lablab (Indian lablab beans) has been carried out to obtain insights into its quaternary association and lectin-carbohydrate interactions. The analysis led to the identification of adenine binding sites at the dimeric interfaces of the heterotetrameric lectin. Structural details of similar adenine binding were reported in only one legume lectin, Dolichos biflorus, before this study. Here, we present the structure of the galactose-binding D. lablab lectin at different pH values in the native form and in complex with galactose and adenine. This first structure report on this lectin also provides a high resolution atomic view of legume lectin-adenine interactions. The tetramer has two canonical and two DB58-like interfaces. The binding of adenine, a non-carbohydrate ligand, is found to occur at four hydrophobic sites at the core of the tetramer at the DB58-like dimeric interfaces and does not interfere with the carbohydrate-binding site. To support the crystallographic observations, the adenine binding was further quantified by carrying out isothermal calorimetric titration. By this method, we not only estimated the affinity of the lectin to adenine but also showed that adenine binds with negative cooperativity in solution. V C 2013 IUBMB Life, 65(7): [633][634][635][636][637][638][639][640][641][642][643][644] 2013

Computational Analysis of the Ligand Binding Site of the Extracellular ATP Receptor, DORN1

“…We found two quaternary structures of L-type lectins (1BJQ and 3UJO) harboring hydrophobic molecules, adenine in a location on the back sheets of a small channel made of two monomers [50,52]. This site is not common in L-type lectins and only known for hydrophobic ligands such as adenine or adenine-derived hormones [53].…”

Are Dietary Lectins Relevant Allergens in Plant Food Allergy?

“…XM_009394597.2], and the Nictaba-related lectin from watermelon Cucumis melo [Acces. NM_001305649.1], was performed with the YASARA Structure program [108] using various protein templates from the PDB, depending on the overall structural scaffold to which they belong (e.g., 1G8W from Phaseolus vulgaris [109], 1LU1 from Dolichos biflorus [101], 3UL2 from Dolichos lablab [110], 3WCS [111] and 5AVA [112] from Phaseolus vulgaris (PHA-E) for modeling the black turtle bean from Phaseolus vulgaris [59], shown in Figures 2 and 3). PROCHECK [113], ANOLEA [114], and the calculated QMEAN scores [115,116] were used to assess the geometric and thermodynamic qualities of the three-dimensional models.…”

X-ray crystallographic studies of the extracellular domain of the first plant ATP receptor, DORN1, and the orthologous protein fromCamelina sativa

“…However, these residues are missing in the extracellular domain of DORN1. In addition to carbohydrate binding, some legume lectins also recognize adenine or adenine-related plant hormones (Shetty et al, 2013;Hamelryck et al, 1999). Adenine is part of ATP; however, it does not compete with ATP for binding to DORN1 (Choi et al, 2014).…”