Banana lectin is unique in its recognition of the reducing unit of 3-O-beta-glucosyl/mannosyl disaccharides: a calorimetric study.
The binding of banana lectin (BanLec) to laminaribiose (Glcbeta1,3Glc) and a series of novel synthetic analogues was measured by titration calorimetry to assess the contribution of the hydroxyl groups of the reducing glycosyl moiety and its 3-O-beta-substituent to binding. Key areas of interaction involved the 1, 2, and 6 positions of the reducing-terminal hexose unit. The alpha-anomeric configuration of the reducing hexose was strongly favored over the beta-anomer. The 2-hydroxyl in the axial position (mannose) also enhanced binding, whereas the 6-hydroxymethyl group was essential, because xylopyranose in the reducing position was inactive. The 3-O-beta-glucosyl unit of methyl alpha-laminaribioside could be replaced by any of its monodeoxy derivatives. However, the 4'-deoxy derivative or axial hydroxy (galactosyl) substitution was somewhat detrimental to binding. 3-O-substitution with the (S)tetrahydropyranyl ring or a benzyl group had similar effect as 4'-deoxyglucosyl substitution. Surprisingly, p-nitrobenzyl or beta-xylosyl 3-O-substitution greatly enhanced binding of the reducing glucosyl or mannosyl derivative. Chemical syntheses of a number of novel disaccharides and analogues prepared for this study are described.
Winter
Harry C
HC
Department of Biological Chemistry, The University of Michigan Medical School, Ann Arbor, MI, USA.
Oscarson
Stefan
S
Slättegård
Rikard
R
Tian
Maozhong
M
Goldstein
Irwin J
IJ
D002151:Calorimetry; D004187:Disaccharides / Q000138:chemical synthesis / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D008358:Mannose / Q000737:chemistry*; D028521:Musa / Q000737:chemistry*; D037121:Plant Lectins / Q000737:chemistry*; D011485:Protein Binding
D004187:Disaccharides; D037121:Plant Lectins; C014637:laminaribiose; D005947:Glucose; D008358:Mannose