Processive DNA synthesis observed in a polymerase crystal suggests a mechanism for the prevention of frameshift mutations.

Journal Article (Journal Article)

DNA polymerases replicate DNA by adding nucleotides to a growing primer strand while avoiding frameshift and point mutations. Here we present a series of up to six successive replication events that were obtained by extension of a primed template directly in a crystal of the thermostable Bacillus DNA polymerase I. The 6-bp extension involves a 20-A translocation of the DNA duplex, representing the largest molecular movement observed in a protein crystal. In addition, we obtained the structure of a "closed" conformation of the enzyme with a bound triphosphate juxtaposed to a template and a dideoxy-terminated primer by constructing a point mutant that destroys a crystal lattice contact stabilizing the wild-type polymerase in an "open" conformation. Together, these observations allow many of the steps involved in DNA replication to be observed in the same enzyme at near atomic detail. The successive replication events observed directly by catalysis in the crystal confirm the general reaction sequence deduced from observations obtained by using several other polymerases and further refine critical aspects of the known reaction mechanism, and also allow us to propose new features that concern the regulated transfer of the template strand between a preinsertion site and an insertion site. We propose that such regulated transfer is an important element in the prevention of frameshift mutations in high-fidelity DNA polymerases. The ability to observe processive, high-fidelity replication directly in a crystal establishes this polymerase as a powerful model system for mechanistic studies in which the structural consequences of mismatches and DNA adducts are observed.

Full Text

Duke Authors

Cited Authors

  • Johnson, SJ; Taylor, JS; Beese, LS

Published Date

  • April 1, 2003

Published In

Volume / Issue

  • 100 / 7

Start / End Page

  • 3895 - 3900

PubMed ID

  • 12649320

Pubmed Central ID

  • PMC153019

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0630532100


  • eng

Conference Location

  • United States