Structures of the major carbohydrates of natural human interleukin‐2

Abstract

Purified human interleukin‐2 secreted by peripheral blood lymphocytes from healthy donors was found to exist in several forms. These forms were (partially) resolved by reversed‐phase high‐performance liquid chromatography and sodium dodecy1 sulfate/polyacrylamide gel electrophoresis. Two major plypeptide species (interleukin‐2 N1 and N2, 16.5 kDa) were shown to be glycosylated on the basis of [3H]galactose/[3H]glucosamine incorporation and determination of amino sugars after acid hydrolysis. A third component (interleukin‐2 M, 14.5 kDa) represents a nonglycosylated form. The amino acid composition and the NH2‐terminal sequence of both forms are consistent with the data deduced from the cDNA coding for interleukin‐2 after removal of a leader peptide of 20 amino acids. Carbohydrates are O‐linked to the IL‐2 protein via threonine‐3 of the polypeptide chain. The ologosaccharides were released by reuctive β‐elimination and were purified by gel filtration and high performance liquid chomatography. Applying methylation analysis, exoglycosidase digestion and fast atom bombardment mass spectrometry the following major carbohydrate structures were identified: N1, NeuAc(α 2‐3) Gal(β 1‐3) GalNAc‐ol; and N2, NeuAc(α 2‐3) Gal(β 1‐3) [NeuAc(α 2‐6)] GalNAc‐ol. Copyright © 1985, Wiley Blackwell. All rights reserved