Disulfide bond erum on 8 Cu2 Cu Most efficient in Figure 1:Structure of IgM.IgM consist of five monomeric subunits,joined by disulfide bridges in both the CHa and CH domains,which are linked to a J chain. chains lack a hinge region but have four,rather than three,CH domains.Each of the subunits have a molecular weight of 180,000 kD.The IgM pentamer posses 10 identical antigen binding sites.About 10%of the normal serum immunoglobulin is of class IgM Structure of Secretory IgG -Carbohydrates 15 kD an not ecretoru protein epithelial cells Figure 1: Structure of IgM. IgM consist of five monomeric subunits, joined by disulfide bridges in both the CH3 and CH4 domains, which are linked to a J chain. µ chains lack a hinge region but have four, rather than three, CH domains. Each of the subunits have a molecular weight of 180,000 kD. The IgM pentamer posses 10 identical antigen binding sites. About 10% of the normal serum immunoglobulin is of class IgM