Structure of S-lectin, a developmentally regulated vertebrate beta-galactoside-binding protein.
The crystal structure of a 14-kDa bovine spleen S-lectin complexed with the disaccharide N-acetyllactosamine at 1.9-A resolution reveals a surprising structural relationship to legume lectins, despite the lack of sequence homology. Two monomers associate to form an extended beta-sandwich, each with the same jelly roll topology typical of legume lectins but with dramatically trimmed loops and with different dimer association. Each monomer binds one N-acetyllactosamine molecule in a topologically and spatially different site than that of legume lectins. The carbohydrate-binding site provides an unprecedented paradigm for carbohydrate binding, with a unique network of salt bridges. The specificity for beta-galactose arises from intricate interactions that constrain the position of the O4 atom.
Liao
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DI
Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville 20850.
Kapadia
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G
Ahmed
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Vasta
G R
GR
Herzberg
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O
D000606:Amino Sugars / Q000737:chemistry*; D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D018360:Crystallography, X-Ray; D005697:Galactosides / Q000737:chemistry*; D037102:Lectins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D037121:Plant Lectins; D011487:Protein Conformation; D013154:Spleen / Q000737:chemistry
D000606:Amino Sugars; D005697:Galactosides; D037102:Lectins; D037121:Plant Lectins; C036292:pea lectin; C000458:N-acetyllactosamine