3.4.22.B14 hanging drop vapor diffusion method, using 0.1-0.18 M (NH4)2SO4, 0.1 M MES (pH 6.5), and 30% (w/v) PEG 5000, at 19°C 3.4.22.B14 in complex with interferon-stimulated gene product 15 proteins from different species 3.4.22.B14 to 2.15 A resolution. PLpro has a short blocking loop BL1-like loop. Access to a conserved catalytic triad consisting of Cys101, His264, and Asp275 is regulated by the flexible loop BL2