WT SHP-1 cells were thawed on ice and resuspended in 10 mL equilibration buffer, consisting of 25 mM Tris pH 8.0, 1 mM DTT, and 200 mM NaCl with 2 mg lysozyme, 0.5 mg/mL aprotinin, 0.7 mg/mL pepstatin A, and 0.5 mg/mL leupeptin. SHP-1 variant cells were thawed and resuspended in 50 mM BisTris pH 6.5, 1 mM EDTA, 3 mM DTT, and 10% glycerol with the same protease inhibitors. The cells were lysed by sonication at 70% amplitude for 30 seconds and then mixed on ice for 1 min and repeated 5-6 times until completely lysed. The cell lysate was centrifuged at 4 °C at 30,000g for 30 min.