Immunoglobulin G molecule

Scallon BJ,Tam SH, McCarthy SG, Cai AN, RajuTS. Higher levels of sialylated Fc glycans in immunoglobulin G molecules Can adversely impact functionality. Mol Immunol 2007 44(7) 1524-34. 

I 18. Immunoglobulin G molecules can be characterized by which of the following statements ... 

Immunoglobulin G (IgG) is the major serum immunoglobulin. Some immunoglobulin G molecules can cross cell membranes and thus can pass between mother and fetus through the placenta, before birth. This is important because the immune system of a fetus is immature and cannot provide adequate protection from disease. Eortunately the IgG acquired from the mother protects the fetus against most bacterial and viral infections that it might encounter before birth. 

Figure 1.2 Structure of an immunoglobulin G molecule (H, heavy chain L, light chain).

FIGURE 1.11 Three -dimensional spacefilling representation of part of a protein molecule, the antigen-binding domain of immunoglobulin G (IgG). Immunoglobulin G is a major type of circulating antibody. Each of the spheres represents an atom in the structure. 

Figure 2 shows the most abundant class of antibodies found in blood serum and lymph - immunoglobulin G (IgG). IgG of molecular mass about 156 000, is most frequently used as a receptor in immunosensors. According to X-ray data6 8, IgG is a Y-shaped molecule consisting of two identical antigen binding Fab arms of dimensions 6.5 nm by 3.5 nm and an inactive Fc shank of dimensions 5 nm by 3.5 nm. 

Figure 14.1. Schematic diagram of the structure of an immunoglobulin G (IgG) molecule. The location and extent of intra- and interchain disulfide bonds varies with the host species and antibody subclass.

Protection and defense. The immune system protects the body from pathogens and foreign substances. An important component of this system is immunoglobulin G (bottom left see p.300). The molecule shown here is bound to an erythrocyte by complex formation with surface glycolipids (see p.292). 

Akerstrom, B. and Bjorck, L., A physiochemical study of protein G, a molecule with unique immunoglobulin G-binding properties, J. Biol. Chem., 261, 10240-10247, 1986. 

At the far left, we can see the nucleic acid and protein structures shown in frame 1. In addition, we show a much larger protein, the immunoglobulin G antibody molecule. Four separate polypeptide chains join to make up an antibody molecule two heavy chains (blue) of about 400 amino acids and two light chains (purple) of about 200 amino acids. The antibody is about 16 nm in width. Finally, at the far right, we show the core particle from a small plant virus, the reovirus. Only the icosahedral protein coat of the virus can be seen. The reovirus particle is about 60 nm across. The nucleic acids of the virus are sequestered inside the virus core. The reovirus family is unusual in that its nucleic acids are all double-stranded RNA molecules. 

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