A large side chain at amino acid 36 of KIR2DL1 prevents constitutive SHP-1 recruitment. (A) Constitutive SHP-1 association with KIR2DL1 in transfected YTS cells monitored by BiFC of reconstituted Venus using flow cytometry. BiFC signal of 2DL1-WT (red) and 2DL1-H36A (top) or 2DL1-H36F (bottom) (blue) is plotted against surface expression, as detected by anti-2DL1-APC binding. (B) Median fluorescence intensity of BiFC signal in the gates shown in panel A. The error bars represent spread in the values of median BiFC signal determined from two independent experiments. (C) Constitutive SHP-1 association with KIR2DL1 in transfected YTS cells monitored by BiFC of reconstituted Venus using confocal microscopy. BiFC signal of 2DL1-WT, 2DL1-H36A, and 2DL1-H36F, determined at the plasma membrane, is plotted. The horizontal and vertical lines represent mean and standard error, respectively.