EMD-0379
Structure of bacteriophage T7 lagging-strand DNA polymerase (D5A/E7A) interacting with primase domains of two gp4 subunits bound to an RNA/DNA hybrid and dTTP (from LagS1)
EMD-0379
Single-particle3.7 Å

Map released: 06/03/2019
Last modified: 06/11/2024
Sample Organism:
Enterobacteria phage T7
Sample: gp5 DNA polymerase and two gp4 primase subunits complexed with trx, RNA/DNA hybrid, and incoming dTTP (from gp4-gp5 lagging-strand complex LagS1)
Fitted models: 6n9u (Avg. Q-score: 0.477)
Deposition Authors: Gao Y
,
Fox T
Sample: gp5 DNA polymerase and two gp4 primase subunits complexed with trx, RNA/DNA hybrid, and incoming dTTP (from gp4-gp5 lagging-strand complex LagS1)
Fitted models: 6n9u (Avg. Q-score: 0.477)
Deposition Authors: Gao Y


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.