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Human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig), an immunosuppressive agent, is a glycoprotein and it was expressed in transgenic rice cell suspension cultures. As a production system, transgenic plant cells have several advantages including low risk of potential contamination with animal pathogens, economical large-scale production, and capacity to carry out most posttranslational modifications (PTMs). Among the PTMs, glycosylation is essential for proteins stability, folding and physiological activity.1, 2) However, there are differences in N-glycosylation between the glycoproteins produced in mammalian and plant cells. N-linked glycan structures contain penultimate galactose and terminal sialic acid residues in mammalian glycoproteins. In the case of plants, in vivo half-life of protein is decreased because of N-linked glycans with plant specific terminal β1, 3-galactose residues.3) To prolong the half-life of plant-made proteins, transgenic rice cells were transformed with human galactosyltransferase gene under the control of the RAmy3D promoter. Consequently, produced target proteins could have glycan structures with not only β1, 3-galactose but also β1, 4-galactose residues at the terminus. In this study, target proteins with terminal β1, 4-galactose oligosaccharides were purified by using Ricinus communis agglutinin (RCA120) lectins that binds to specific β1, 4-glactose structures. Through the purification process by RCA120 affinity chromatography, it was
confirmed that N-linked glycan structures of hCTLA4Ig was modified similar to that of
mammalian glycoproteins in transformed rice cells.