Binding characteristics of galactoside-binding lectin (galaptin) from human spleen.
J Biol Chem
; 265(14): 7864-71, 1990 May 15.
Article
em En
| MEDLINE
| ID: mdl-2335508
ABSTRACT
Binding characteristics of human spleen soluble galactoside-binding protein (galaptin) were studied using simple galactosides, galactose-terminated disaccharides, cluster glycosides containing up to 6 terminal lactosyl residues, bovine serum albumin derivatives containing 7 to 40 lactosyl residues, desialylated serum glycoproteins, and glycopeptides derived thereof as inhibitors in a newly developed binding assay. In this assay, aminohexyl lactoside was attached to divinyl sulfone-activated Sepharose, which was then used to bind 125I-galaptin. Similarly derivatized Sepharose containing mannoside served as a control. The assay is sensitive, maintains linearity in the concentration range of 125I-galaptin tested, and has very low nonspecific binding. The following new findings were made. 1) All the alpha-D-galactopyranosides with non-sugar aglycon were better inhibitors than the corresponding beta-D-galactopyranoside. 2) The S-galactosides were better inhibitors than the corresponding O-galactosides, regardless of the anomeric configuration. 3) Many Gal beta 1-4- and Gal beta 1-3-linked disaccharides were tested. Although the galaptin did not appear to recognize N-acetylglucosamine as a monosaccharide, the presence of this sugar penultimate to galactose increased the binding affinity by as much as 500-fold, as was the case for N-acetyllactosamine. Of a particular importance is the presence of an equatorial 3-OH group on this sugar. We synthesized the 3-deoxy derivative of N-acetyllactosamine and found that it had 50-fold lower binding affinity compared to N-acetyllactosamine. 4) The binding sites of this lectin do not seem to be operating in a cooperative fashion, since synthetic lactose-containing divalent ligands with various inter-galactose distances did not increase the binding affinity significantly.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Baço
/
Hemaglutininas
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
1990
Tipo de documento:
Article