Toxin secreted by the type VI (T6SS) secretion system that acts on prokaryotic target cells. Acts in conjunction with VasW, an accessory protein to VasX, to compromise the inner membrane of prokaryotic target cells. Delivered to the target cell by the type VI (T6SS) secretion system. Deletion of vasX gene together with deletion of vgrG3 fail to kill Escherichia coli.