EMD-0395
Structure of bacteriophage T7 leading-strand DNA polymerase (D5A/E7A)/Trx and of gp4 (E343Q) bound to a DNA fork (Lead5)
EMD-0395
Single-particle13.8 Å
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Map released: 06/03/2019
Last modified: 06/03/2019
Sample Organism:
Enterobacteria phage T7,
Escherichia coli
Sample: T7 DNA polymerase/Trx interacting with C-terminal tail of helicase domains B of T7 helicase (gp4) in complex with a fork DNA substrate and dTTP (from gp4-gp5 leading-strand complex Lead5)
Deposition Authors: Gao Y, Fox T, Val N, Yang W
Sample: T7 DNA polymerase/Trx interacting with C-terminal tail of helicase domains B of T7 helicase (gp4) in complex with a fork DNA substrate and dTTP (from gp4-gp5 leading-strand complex Lead5)
Deposition Authors: Gao Y, Fox T, Val N, Yang W
Structures and operating principles of the replisome.
Abstract:
Visualization in atomic detail of the replisome that performs concerted leading- and lagging-DNA strand synthesis at a replication fork has not been reported. Using bacteriophage T7 as a model system, we determined cryo-electron microscopy structures up to 3.2-angstroms resolution of helicase translocating along DNA and of helicase-polymerase-primase complexes engaging in synthesis of both DNA strands. Each domain of the spiral-shaped hexameric helicase translocates sequentially hand-over-hand along a single-stranded DNA coil, akin to the way AAA+ ATPases (adenosine triphosphatases) unfold peptides. Two lagging-strand polymerases are attached to the primase, ready for Okazaki fragment synthesis in tandem. A β hairpin from the leading-strand polymerase separates two parental DNA strands into a T-shaped fork, thus enabling the closely coupled helicase to advance perpendicular to the downstream DNA duplex. These structures reveal the molecular organization and operating principles of a replisome.
Visualization in atomic detail of the replisome that performs concerted leading- and lagging-DNA strand synthesis at a replication fork has not been reported. Using bacteriophage T7 as a model system, we determined cryo-electron microscopy structures up to 3.2-angstroms resolution of helicase translocating along DNA and of helicase-polymerase-primase complexes engaging in synthesis of both DNA strands. Each domain of the spiral-shaped hexameric helicase translocates sequentially hand-over-hand along a single-stranded DNA coil, akin to the way AAA+ ATPases (adenosine triphosphatases) unfold peptides. Two lagging-strand polymerases are attached to the primase, ready for Okazaki fragment synthesis in tandem. A β hairpin from the leading-strand polymerase separates two parental DNA strands into a T-shaped fork, thus enabling the closely coupled helicase to advance perpendicular to the downstream DNA duplex. These structures reveal the molecular organization and operating principles of a replisome.