Figure 4.

Cell‐based co‐immunoprecipitation (A–C) and decrease intracellular pH (D) by SARS‐CoV 3CL^pro protease. The cell lysates of 3CL^pro‐expressing cells and mock cells were immunoprecipitated by anti‐His tag to 3CL^pro. The immunoprecipitate was analyzed using Coomassie blue staining (A), and Western blotting with anti‐His tag antibody to 3CL^pro (B) and chicken anti‐V‐ATPase G1 polyclonal antibody (C). In addition, the 3CL^pro‐expressing cells and mock cells were incubated with 20 μM carboxy SNARF‐1 for 30 min at room temperature. A dual‐emission ration at 580 and 640 nm of intracellular dye was detected using a fixed excitation at 514 nm, and then converted to intracellular pH (D).