Involvement of the zinc-binding capacity of Sendai virus V protein in viral pathogenesis

The V protein of Sendai virus (SeV) is nonessential to virus replication in cell culture but indispensable to viral pathogenicity in mice. The highly conserved cysteine-rich zinc finger-like domain in its carboxyl terminus is believed to be responsible for this viral pathogenicity. in the present st udy, we showed that the cysteine-rich domain of the SeV V protein could act ually bind zinc by using glutathione-S-transferase fusion proteins. When th e seven conserved cysteine residues at positions 337, 341, 353, 355, 358, 3 62, and 365 were replaced individually, the zinc-binding capacities of the mutant proteins were greatly impaired, ranging from 22 to 68% of that of th e wild type. We then recovered two mutant SeVs from cDNA, which have V-C341 S and V-C365R mutations and represent maximal and minimal zinc-binding capa cities among the corresponding mutant Fusion proteins, respectively. The mu tant viruses showed viral protein synthesis and growth patterns similar to those of wild-type SeV in cultured cells. However, the mutant viruses were strongly attenuated in mice in a way similar to that of SeV V-Delta C, whic h has a truncated V protein lacking the cysteine-rich domain, by exhibiting earlier viral clearance from the mouse lung and less virulence to mice. We therefore conclude that the zinc-binding capacity of the V protein is invo lved in viral pathogenesis.