A structural basis for four distinct elution profiles on concanavalin A – Sepharose affinity chromatography of glycopeptides

Abstract

Twelve 14C-acetylated glycopeptides have been subjected to affinity chromatography on concanavalin A (Con A) – Sepharose at pH 7.5. The elution profiles could be classified into four distinct patterns. The first pattern showed no retardation of glycopeptide on the column and was elicited with a glycopeptide having three peripheral oligosaccharide chains:[Formula: see text]Such glycopeptides have only a single mannose residue capable of interacting with Con A – Sepharose; an interacting mannose residue is either an α-linked nonreducing terminal residue or an α-linked 2-O-substituted residue. The second type of profile showed a retarded elution of glycopeptide with buffer lacking methyl α-D-glucopyranoside (indicative of weak interaction with the column) and was given by glycopeptides with the structures:[Formula: see text]where R1 is either H or a sialyl residue. The third profile type showed tight binding of glycopeptide to Con A – Sepharose and elution as a sharp peak with 0.1 M methyl α-D-glucopyranoside; glycopeptides giving this pattern had the structures:[Formula: see text]where R2 is either H, GlcNAc, Gal-β1,4-GlcNAc, or sialyl-Gal-β1,4-GlcNAc. These glycopeptides all have two interacting mannose residues, the minimum required for binding to the column; one of these mannose residues must, however, be a terminal residue to obtain tight binding and sharp elution. The fourth profile type showed tight binding of glycopeptide to the column but elution with 0.1 M methyl α-D-glucopyranoside resulted in a broad peak indicating very tight binding; glycopeptides showing this behaviour had the structures:[Formula: see text]where R3 is either GlcNAc, Gal-β1,4-GlcNAc, or siaryl-Gal-β1,4-GlcNAc. Therefore it can be concluded that although a minimum of two interacting mannose residues is required for binding to Con A – Sepharose, the residues linked to these mannoses can either strengthen or weaken binding to the column.