Figure 2: Comparison of the binding of SAP and IgG to the FcγRIIA molecule. The structure of the IgG-FcγRIIA is shown on the left and is based on the NCBI entry 3RY6. The structure of the SAP-FcγRIIA complex taken from the NCBI entry 3D5O is shown on the right [14]. The FcR interaction with SAP engages the ridge helices of two nonadjacent protomers, resulting in a one-to-one stoichiometry.