Expression, crystallization and preliminary X-ray diffraction analysis of human paired Ig-like type 2 receptor α (PILRα)

Human paired immunoglobulin-like (Ig-like) type 2 receptor α (PILRα) is a type I membrane protein that is mainly expressed in immune-related cells such as monocytes, granulocytes and dendritic cells. PILRα can suppress the functions of such immune cells because it has the immunoreceptor tyrosine-based inhibitory motif (ITIM) in the intracellular region, which recruits the phosphatase Src homology-2 (SH2) domain-containing protein tyrosine phosphatase 2 (SHP-­2) to inhibit phophorylations induced by activation signals. The extracellular region of human PILRα comprises one immuno­globulin superfamily V-set domain and a stalk region. The V-set domain (residues 13–131) of human PILRα was overexpressed in Escherichia coli as inclusion bodies, refolded by rapid dilution and purified. The PILRα protein was successfully crystallized at 293 K using the sitting-drop vapour-diffusion method. The crystals diffracted to 1.3 Å resolution at SPring-8 BL41XU; they belong to space group P2₁2₁2₁, with unit-cell parameters a = 40.4, b = 45.0, c = 56.9 Å, and contain one molecule per asymmetric unit.