Crystallization and Data Collection
MERS-CoV N-NTD crystals were grown as previously described:46 MERS-CoV N-NTD was crystallized at room temperature (∼25 °C) by the sitting-drop vapor-diffusion method. A protein solution (2 μL; 10 mg mL–1) was mixed with an equal volume of crystallization solution consisting of 75 mM ammonium sulfate, 2 mM NaBr, and 29% PEG 3350 (Sigma-Aldrich Corp., St. Louis, MO) and equilibrated against a 300 μL solution. MERS-CoV N-NTD:P3 co-crystals were obtained using a crystallization solution containing 2 mM P3. MERS-CoV N-NTD crystals in complex with P1 were obtained by soaking native MERS-CoV N-NTD crystals for 90 s at room temperature in a crystallization solution containing 2 mM P1. Diffraction datasets for MERS-CoV N-NTD alone and in complex with P1 were collected at beamline 13B1 of the Taiwan Light Source (TLS) of the National Synchrotron Research Center (NSRRC; Hsinchu City, Taiwan). Diffraction of the MERS-CoV N-NTD:P3 complex was performed at the beamline SP44XU of SPring-8 (Hyogo, Japan).