Fractionation of Fab glycosylated immunoglobulin G with concanavalin A chromatography unveils new structural properties of the molecule

// Tao Huang 1, * , Xueling Chen 1, * , Huan Gu 1 , Conghui Zhao 2, 3 , Xingmu Liu 1, 4 , Meiling Yan 1 , Xiaodong Deng 1 , Zaiping Zhang 1 , Jiang Gu 1, 3 1 Department of Pathology and Provincial Key Laboratory of Infectious Diseases and Immunopathology, Collaborative and Creative Center, Molecular Diagnosis and Personalized Medicine, Shantou University Medical College, Shantou, Guangdong, 515041, China 2 Department of Oral Pathology, Beijing Stomatological Hospital, Capital Medical University, Beijing, 100050, China 3 Department of Pathology, Beijing University Health Science Center, Beijing, 100083, China 4 Department of General Surgery, Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong, 515041, China * These authors contributed equally to this work Correspondence to: Jiang Gu, e-mail: 2523381625@qq.com Keywords: IgG, glycosylation, ConA, asymmetry, symmetry Received: February 25, 2016      Accepted: April 11, 2016      Published: April 28, 2016 ABSTRACT Concanavalin A (ConA) chromatography has been extensively used to separate asymmetric Immunoglobulin G (IgG), which possesses oligosaccharide attached to one of the two F(ab’) 2 arms, from symmetric IgG with no glycan attached to Fab fragments. In this study, applying affinity chromatography, silver stain, Western blot and lectin stain techniques, N- linked oligosaccharide attached to Fab fragment was demonstrated to be exposed on the surface of the protein and be accessible by ConA. In contrast, N- linked oligosaccharide attached to asparagine (Asn) 297 of IgG Fc was located in the inside of the natural protein and was inaccessible by ConA. In addition to asymmetric IgG, there are also detectable level of IgG with both F(ab’) 2 arms glycosylated that has not been reported previously. The discoveries of new basic molecular structure of IgG would have implications in understanding the function and properties of this important immune molecule with clinical applications.