The domain structure of Helicobacter pylori DnaB helicase: the N-terminal domain can be dispensable for helicase activity whereas the extreme C-terminal region is essential for its function.
Hexameric DnaB type replicative helicases are essential for DNA strand unwinding along with the direction of replication fork movement. These helicases in general contain an amino terminal domain and a carboxy terminal domain separated by a linker region. Due to the lack of crystal structure of a full-length DnaB like helicase, the domain structure and function of these types of helicases are not clear. We have reported recently that Helicobacter pylori DnaB helicase is a replicative helicase in vitro and it can bypass Escherichia coli DnaC activity in vivo. Using biochemical, biophysical and genetic complementation assays, here we show that though the N-terminal region of HpDnaB is required for conformational changes between C6 and C3 rotational symmetry, it is not essential for in vitro helicase activity and in vivo function of the protein. Instead, an extreme carboxy terminal region and an adjacent unique 34 amino acid insertion region were found to be essential for HpDnaB activity suggesting that these regions are important for proper folding and oligomerization of this protein. These results confer great potential in understanding the domain structures of DnaB type helicases and their related function.
Nitharwal
Ram Gopal
RG
Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India.
Paul
Subhankar
S
Dar
Ashraf
A
Choudhury
Nirupam Roy
NR
Soni
Rajesh K
RK
Prusty
Dhaneswar
D
Sinha
Sukrat
S
Kashav
Tara
T
Mukhopadhyay
Gauranga
G
Chaudhuri
Tapan Kumar
TK
Gourinath
Samudrala
S
Dhar
Suman Kumar
SK
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053488:DnaB Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D016480:Helicobacter pylori / Q000201:enzymology*; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D040681:Structural Homology, Protein
D001426:Bacterial Proteins; C506730:dnaB protein, E coli; D053488:DnaB Helicases