Specificity of chicken liver carbohydrate binding protein

Abstract

Chicken hepatic lectin was isolated, with affinity chromatography, by using neoglycoproteins of bovine serum albumin (BSA) to which n moles of glycosides were attached, by amidination (Glycn-AI-BSA), to Sepharose 4B. The same protein could be isolated from Man-, GlcNAc- and Glc-AI-BSA-Sepharose columns, and it was identical to the protein previously reported . The sugar specificity for binding to the isolated chicken hepatic lectin examined with Glycn-AI-BSA showed the order of potency for binding Glycn-AI-BSA to be: D-GlcNAc > D-Glc, D-Man, L-Fuc > D-Gal. The estimated Ki''s for binding of GlcNAc36-AI-BSA, Glc37-AI-BSA, Man33-AI-BSA and L-Fuc28-AI-BSA were (6-20) .times. 10-11, (2-3) .times. 10-8, (3-9) .times. 10-8 and 5 .times. 10-8 M, respectively. The binding requirements of the binding protein were studied with a wide variety of Glycn-BSA with different sugars and aglyconic linkages, as well as simple sugars and glycosides. It was concluded that: GlcNAc is the most potent sugar for binding; the requirement for C-2 substituents is flexible; an equatorial OH group at C-3 and C-4 must be present; the 5-CH2OH group is not required for binding; the lectin cannot accommodate a negative charge at C-6; and D-Man and L-Fuc bind equally well. Unlike the mammalian hepatic lectin, the chicken hepatic lectin has little preference for the type of sugar to protein linkage group.