Immunoglobulin hinge region

Figure 1S.6 Enzymatic cleavage of immunoglobulin IgG. The enzyme papain splits the molecule in the hinge region, yielding two Fab fragments and one Fc fragment.

IgG antibody molecules are composed of two light chains and two heavy chains joined together by disulfide bonds. Each light chain has one variable domain and one constant domain, while each heavy chain has one variable and three constant domains. All of the domains have a similar three-dimensional structure known as the immunoglobulin fold. The Fc stem of the molecule is formed by constant domains from each of the heavy chains, while two Fab arms are formed by constant and variable domains from both heavy and light chains. The hinge region between the stem and the arms is flexible and allows the arms to move relative to each other and to the stem. 

The following protocol is based on the methods recommended by Thermo Fisher for use of the cyanine dye DyLight 649. Antibody reduction is based on the methods of Sun et al. (2005), which results in partially reduced bispecific immunoglobulin containing available thiols in the hinge region for labeling. 

Tan LK, Shopes RJ, Oi VT, Morrison SL. Influence of the hinge region on complement activation, Clq binding, and segmental flexibility in chimeric human immunoglobulins. Proc Natl Acad Sci USA 1990 87(l) 162-6. 

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