1q57
From Proteopedia
The Crystal Structure of the Bifunctional Primase-Helicase of Bacteriophage T7
Overview
Within minutes after infecting Escherichia coli, bacteriophage T7 synthesizes many copies of its genomic DNA. The lynchpin of the T7 replication system is a bifunctional primase-helicase that unwinds duplex DNA at the replication fork while initiating the synthesis of Okazaki fragments on the lagging strand. We have determined a 3.45 A crystal structure of the T7 primase-helicase that shows an articulated arrangement of the primase and helicase sites. The crystallized primase-helicase is a heptamer with a crown-like shape, reflecting an intimate packing of helicase domains into a ring that is topped with loosely arrayed primase domains. This heptameric isoform can accommodate double-stranded DNA in its central channel, which nicely explains its recently described DNA remodeling activity. The double-jointed structure of the primase-helicase permits a free range of motion for the primase and helicase domains that suggests how the continuous unwinding of DNA at the replication fork can be periodically coupled to Okazaki fragment synthesis.
About this Structure
1Q57 is a Single protein structure of sequence from Enterobacteria phage t7. Full crystallographic information is available from OCA.
Reference
The crystal structure of the bifunctional primase-helicase of bacteriophage T7., Toth EA, Li Y, Sawaya MR, Cheng Y, Ellenberger T, Mol Cell. 2003 Nov;12(5):1113-23. PMID:14636571 Page seeded by OCA on Sat May 3 05:52:42 2008
