Structures of the complexes of peanut lectin with methyl-beta-galactose and N-acetyllactosamine and a comparative study of carbohydrate binding in Gal/GalNAc-specific legume lectins.
The crystal structures of complexes of peanut lectin with methyl-beta-galactose and N-acetyllactosamine have been determined at 2.8 and 2.7 A, respectively. These, and the complexes involving lactose and the T-antigenic disaccharide reported previously, permit a detailed characterization of peanut-lectin-carbohydrate association and the role of water molecules therein. The water molecules in the combining site are substantially conserved in the four complexes. The role of interacting sugar hydroxyl groups, when absent, are often mimicked by ordered water molecules not only at the primary combining site, but also at the site of the second sugar ring. The similarity of peanut-lectin-sugar interactions with those in other galactose/N-acetylgalactosamine-specific lectins also extend to a substantial degree to water bridges. The comparative study provides a structural explanation for the exclusive specificity of peanut lectin for galactose at the monosaccharide level, compared with that of the other lectins for galactose as well as N-acetylgalactosamine. The complexes also provide a qualitative structural rationale for differences in the strengths of binding of peanut lectin to different sugars.
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
R
R
Ravishankar
K
K
Suguna
A
A
Surolia
M
M
Vijayan
D000606:Amino Sugars / Q000737:chemistry*; D001665:Binding Sites; D002241:Carbohydrates / Q000737:chemistry; D018360:Crystallography, X-Ray; D046911:Macromolecular Substances; D008756:Methylgalactosides / Q000737:chemistry*; D008958:Models, Molecular; D019887:Peanut Agglutinin / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014867:Water / Q000737:chemistry
D000606:Amino Sugars; D002241:Carbohydrates; D046911:Macromolecular Substances; D008756:Methylgalactosides; D019887:Peanut Agglutinin; D014867:Water; C000458:N-acetyllactosamine