Studies of the binding specificity of concanavalin A. Nature of the extended binding site for asparagine-linked carbohydrates.
In the preceding paper [Mandal, D. K., Kishore, N., & Brewer, C. F. (1994) Biochemistry (preceding paper in this issue)] the trisaccharide 3,6-di-O-(alpha-D-mannopyranosyl)-D-mannose, which is present in all asparagine-linked carbohydrates, was shown by titration microcalorimetry to bind to the lectin concanavalin A (Con A) with nearly -6 kcal mol-1 greater enthalpy change (delta H) than methyl alpha-D-mannopyranoside (Me alpha Man). These results indicate that Con A possesses an extended binding site for the trisaccharide. In the present paper, we have investigated the binding of a series of synthetic analogs of the methyl alpha-anomer of the trisaccharide using hemagglutination inhibition, solvent proton magnetic relaxation dispersion (NMRD), near ultraviolet circular dichroism, and titration microcalorimetry measurements. Four of the analogs tested possess an alpha-glucosyl or alpha-galactosyl residue substituted at either the alpha(1-6) or alpha(1-3) position. Analysis of the data indicates that the alpha(1-6) residue of the parent trimannoside binds to the so-called monosaccharide site and the alpha(1-3) residue to a weaker secondary site. Binding at the secondary site involves unfavorable interactions of the 2-equatorial hydroxyl of the alpha(1-3) Glc derivative since this analog binds with 12-fold lower affinity and -3.4 kcal mol-1 lesser delta H than the trimannoside, whereas the alpha(1-3)-2-deoxyGlc analog possesses essentially the same affinity and delta H as the trimannoside.(ABSTRACT TRUNCATED AT 250 WORDS)
Mandal
D K
DK
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461.
Bhattacharyya
L
L
Koenig
S H
SH
Brown
R D
RD
Oscarson
S
S
Brewer
C F
CF
D001216:Asparagine / Q000378:metabolism*; D001665:Binding Sites; D002151:Calorimetry / Q000379:methods; D050260:Carbohydrate Metabolism; D002240:Carbohydrate Sequence; D002942:Circular Dichroism; D003208:Concanavalin A / Q000378:metabolism*; D006386:Hemagglutination Tests; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D003208:Concanavalin A; D001216:Asparagine