Purification, crystallization and X-ray diffraction analysis of the extracellular part of the human Fc receptor for IgA, FcαRI (CD89)

FcαRI is the predominant receptor for IgA in the serum. Nevertheless, the interaction between the molecules that finally leads to an immune response is poorly understood. To investigate the structural requirements for IgA binding, the extracellular region of FcαRI was cloned and overexpressed in Escherichia coli. The resulting inclusion-body protein was refolded and purified. Despite its deglycosylated state, this recombinant FcαRI retained its ability to bind human IgA. The protein crystallized spontaneously as microcrystalline needles. Recrystallization yielded crystals belonging to a primitive monoclinic space group. A complete 2.8 Å resolution X-ray diffraction data set was collected using synchrotron radiation.