Vol. 42, No. 4, July 1997 BIOCHEMISTRY and MOLECULAR BIOLOGY INTERNATIONAL Pages769-778 THE STRUCTURAL ANALYSIS OF THE O-GLYCANS OF THE JACALIN-BOUND RABBIT IMMUNOGLOBULIN G S. Kabir* and G.J. Gerwig Bijvoet Center, Department of Bio-Organic Chemistry, Utrecht University, P.O.Box 80 075, NL-3508 TB Utrecht, The Netherlands Received April 21, 1997 SUMMARY Rabbit immunoglobulin G (IgG) is a sialoglycoprotein (2.4% carbohydrate), containing both N-glycolyl (Neu5Gc) and N-acetyl (NeuSAc) neuraminic acids in a ratio of 87:13. A small fraction of rabbit IgG (about 25% of total IgG) bound to jacalin as demonstrated by affinity chromatography. The jacalin-bound rabbit IgG contained O-linked glycans which were liberated from the protein by f~-elimination and isolated. Two O-glycan structures were determined by 1H-NtVIR spectroscopy, as being NeuSGc(R2-3)-Gal (t31-3)-GalNAc-ol and Neu5Ac(ct2-3)-Gal(B1-3)-GalNAc-ol in a ratio of 83:17. INTRODUCTION The jackfruit (Artocarpus heterophyllus) is a tropical plant and its seeds are consumed by humans. The mature seeds contain high levels of a lectin, termed jacalin, that specifically binds human immunoglobulin A (IgA), subclass specificity being restricted to IgA1 [1]. Jacalin does not bind human immunoglobulin G (IgG). Also, jacalin does not bind IgA from various mammalian species such as pig, goat, horse, cow and dog as evidenced by affinity chromatography on immobilized jacalin [2]. However, jacalin binds rabbit IgA and has been used to isolate secretory IgA from rabbit intestines [3]. In addition, it has been observed that rabbit IgG was heterogeneous with *Correspondence to: Dr. S. Kabir, Academic Research and Information Services, Tobaksspinnargatan 5, 117 36 Stockholm, Sweden 1039-9712/97/040769-10505.00/0 Copyright 9 1997 by Academic Press Australia. 769 All rights of reproduction in any form reserved.