Characterization of Glycoproteins with the Immunoglobulin Fold by X-Ray Crystallography and Biophysical Techniques
1Institute of Applied Biosciences, Centre for Research and Technology Hellas, 2Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, 3Department of Molecular Medicine and Surgery, Karolinska Institutet, 4Division of Immunology, Transplantation and Infectious, IRCCS San Raffaele Scientific Institute, 5Department of Immunology, Laboratory for Medical Immunology, Erasmus University Medical Center, 6Hematology Department, Nikea General Hospital, 7Assistance publique - Hôpitaux de Paris (AP-HP), Hopital Pitié-Salpêtrière, Department of Hematology, and UPMC University Paris 06, UMRS 1138, 8Division of Experimental Oncology, IRCCS Istituto Scientifico San Raffaele and Università Vita-Salute San Raffaele
1Department of Medicine, Weill Cornell Medical College, 2Institute for Computational Biomedicine, Weill Cornell Medical College, 3Department of Pathology and Laboratory Medicine, Weill Cornell Medical College
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.
Antibodies consist of four polypeptide chains: two identical heavy chains of approximately 440 amino acids each, and two identical light chains composed of roughly 220 amino acids each. These chains are arranged in a Y-shaped structure that is held together by a combination of covalent disulfide bonds and noncovalent bonds. Furthermore, most antibodies carry sugar residues. The process of adding sugar side chains to a protein is called glycosylation. Both the light chain and heavy chain contribute to the antigen binding site at each of the tips of the Y structure. These 110-130 amino acids are highly variable to allow recognition of an almost unlimited number of antigens. This region is also called the variable region and is part of the antigen binding fragment. Each arm of the Y-shaped unit carries an identical antigen binding site. Antibodies can crosslink antigens: when one arm binds to one antigen and the other arm binds to a second, structurally identical antigen. Crosslinking is facilitated by the f…
1Department of Chemistry, Hunter College of the City University of New York, 2Ph.D. Program in Chemistry, Graduate Center of the City University of New York, 3Department of Radiology, Memorial Sloan Kettering Cancer Center, 4Department of Radiology, Weill Cornell Medical College