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Nat Chem Biol. 2009 Dec;5(12):904-12. doi: 10.1038/nchembio.236. Epub 2009 Oct 18.

Coupling DNA unwinding activity with primer synthesis in the bacteriophage T4 primosome.

Author information

1
Université Pierre et Marie Curie Paris, Université Paris Diderot, Centre National de la Recherche Scientifique, France.

Abstract

The unwinding and priming activities of the bacteriophage T4 primosome, which consists of a hexameric helicase (gp41) translocating 5' to 3' and an oligomeric primase (gp61) synthesizing primers 5' to 3', have been investigated on DNA hairpins manipulated by a magnetic trap. We find that the T4 primosome continuously unwinds the DNA duplex while allowing for primer synthesis through a primosome disassembly mechanism or a new DNA looping mechanism. A fused gp61-gp41 primosome unwinds and primes DNA exclusively via the DNA looping mechanism. Other proteins within the replisome control the partitioning of these two mechanisms by disfavoring primosome disassembly, thereby increasing primase processivity. In contrast to T4, priming in bacteriophage T7 and Escherichia coli involves discrete pausing of the primosome and dissociation of the primase from the helicase, respectively. Thus nature appears to use several strategies to couple the disparate helicase and primase activities within primosomes.

PMID:
19838204
PMCID:
PMC2784132
DOI:
10.1038/nchembio.236
[Indexed for MEDLINE]
Free PMC Article

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