Binding interaction of SARS coronavirus 3CL(pro) protease with vacuolar‐H(+) ATPase G1 subunit

The pathogenesis of severe acute respiratory syndrome coronavirus (SARS‐CoV) is an important issue for treatment and prevention of SARS. Recently, SARS‐CoV 3CL(pro) protease has been implied to be possible relevance to SARS‐CoV pathogenesis. In this study, we intended to identify potential 3CL(pro)‐interacting cellular protein(s) using the phage‐displayed human lung cDNA library. The vacuolar‐H(+) ATPase (V‐ATPase) G1 subunit that contained a 3CL(pro) cleavage site‐like motif was identified as a 3CL(pro)‐interacting protein, as confirmed using the co‐immunoprecipitation assay and the relative affinity assay. In addition, our result also demonstrated the cleavage of the V‐ATPase G1 fusion protein and the immunoprecipitation of cellular V‐ATPase G1 by the 3CL(pro). Moreover, loading cells with SNARF‐1 pH‐sensitive dye showed that the intracellular pH in 3CL(pro)‐expressing cells was significantly lower as compared to mock cells.