We have described a novel essential replicative
DNA helicase from Bacillus anthracis, the identification of its gene, and the elucidation of its enzymatic characteristics.
Anthrax DnaB helicase (DnaB(BA)) is a 453-amino-acid, 50-kDa
polypeptide with
ATPase and
DNA helicase activities. DnaB(BA) displayed distinct enzymatic and kinetic properties. DnaB(BA) has low
single-stranded DNA (
ssDNA)-dependent ATPase activity but possesses a strong 5'-->3'
DNA helicase activity. The stimulation of
ATPase activity appeared to be a function of the length of the ssDNA template rather than of ssDNA binding alone. The highest specific activity was observed with M13mp19 ssDNA. The results presented here indicated that the
ATPase activity of DnaB(BA) was coupled to its migration on an ssDNA template rather than to
DNA binding alone. It did not require
nucleotide to bind ssDNA. DnaB(BA) demonstrated a strong
DNA helicase activity that required
ATP or dATP. Therefore, DnaB(BA) has an attenuated
ATPase activity and a highly active
DNA helicase activity. Based on the ratio of
DNA helicase and
ATPase activities, DnaB(BA) is highly efficient in
DNA unwinding and its coupling to
ATP consumption.