Crystallization and preliminary crystallographic analysis of winged bean acidic lectin.

The acidic lectin (WBAII) from the winged bean (Psophocarpus tetragonolobus) binds to the H-antigenic determinant on human erythrocytes and to the T-antigenic disaccharide Gal-beta1,3-GalNAc. Two crystal forms of WBAII were obtained in the presence of methyl-alpha-D-galactose. Form I belongs to space group R3 with unit-cell dimensions a = b = 182.11, c = 44.99 A and has one dimer in the asymmetric unit. Form II belongs to space group C2 with unit-cell dimensions a = 135.36, b = 127.25, c = 139.98 A, beta = 95. 9 degrees and has four dimers in the asymmetric unit. Intensity data were collected to 3.0 A and to 3.5 A from crystals of form I and II, respectively. The structures were solved by the molecular-replacement method using the coordinates of the basic form of winged bean lectin.

Differential scanning calorimetric studies of the glycoprotein, winged bean acidic lectin, isolated from the seeds of Psophocarpus tetrogonolobus.

Differential scanning calorimetry of solutions of WBAII and in presence of sugar ligands shows that WBAII dimer dissociates to its constituent monomeric subunits at the denaturation temperature. The thermal denaturation of WBAII consists of the unfolding of two independent domains of WBAII similar to that of basic winged bean lectin and ECorL and in contrast to concanavalin A (conA), pea and lentil lectin, which unfold as single entities. Apparently, the glycosylation reduces the structural integrity of WBAII as compared to conA, pea and lentil lectin. The increase in the denaturation temperature of the sugar-lectin complexes yields binding constants close to the binding constants extrapolated from the ITC results and confirms the mechanism proposed for its thermal unfolding.

Localized agglutinin staining in muscle capillaries from normal and very old atrophic human muscle using winged bean (Psophocarpus tetragonolobus) lectin.

The winged bean (Psophocarpus tetragonolobus) agglutinin (total lectin) and its basic (WBA I) and acidic isoform (WBA II) were used to analyze capillaries in sections from human muscle. The microvessels were clearly labeled after incubation with the lectins in both normal muscle and in old muscles with age-related type II atrophy or muscle fiber grouping. Muscle fibers, nerves, and connective tissue remained unstained. The total lectin detected muscle capillaries from all blood group AB0 individuals. The isoform WBA I reacted only with blood vessels in blood group A and B individuals, while the blood vessels in blood group 0 individuals were demonstrated with WBA II. WBA I staining was inhibited by p-nitrophenyl alpha-galactopyranoside and N-acetylgalactosamine, whereas 2'-fucosyllactose and preincubation with an antibody against type-1 chain H abolished capillary staining with WBA II. The study demonstrates the usefulness of WBA as a marker of capillaries in human muscle.

On the relationship of thermodynamic parameters with the buried surface area in protein-ligand complex formation.

Prediction of thermodynamic parameters of protein-protein and antigen-antibody complex formation from high resolution structural parameters has recently received much attention, since an understanding of the contributions of different fundamental processes like hydrophobic interactions, hydrogen bonding, salt bridge formation, solvent reorganization etc. to the overall thermodynamic parameters and their relations with the structural parameters would lead to rational drug design. Using the results of the dissolution of hydrocarbons and other model compounds the changes in heat capacity (delta C(p)), enthalpy (delta H) and entropy (delta S) have been empirically correlated with the polar and apolar surface areas buried during the process of protein folding/unfolding and protein-ligand complex formation. In this regard, the polar and apolar surfaces removed from the solvent in a protein-ligand complex have been calculated from the experimentally observed values of changes in heat capacity (delta C(p)) and enthalpy (delta H) for protein-ligand complexes for which accurate thermodynamic and high resolution structural data are available, and the results have been compared with the x-ray crystallographic observations. Analyses of the available results show poor correlation between the thermodynamic and structural parameters. Probable reasons for this discrepancy are mostly related with the reorganization of water accompanying the reaction which is indeed proven by the analyses of the energetics of the binding of the wheat germ agglutinin to oligosaccharides.