High Resolution Image of DNA Repair Enzyme

Researchers have succeeded in preparing a three-dimensional image with two-angstrom resolution of the helicase enzyme from the T4 bacteriophage. Helicase is an enzyme that binds ahead of the replicating fork in the discontinuous replication of DNA and catalyzes the energy-dependent unwinding of the duplex. The enzyme has ATPase activity and hydrolyzes two molecules of ATP (adenotriphosphate) per DNA base pair broken.

In bacteriophage T4 a system comprising three proteins--the RecA-like recombination protein UvsX, a recombination mediator protein UvsY, and a helicase UvsW--repairs DNA damage by a process that involves homologous recombination. Investigators at St. Jude Children's Research Hospital (Memphis, TN, USA) used a modified form of x-ray crystallography to create images of UvsW. In the April 2004 issue of Structure they described the two-angstrom resolution crystal structure of the N-terminal two domains of the UvsW helicase (residues 1–282). The structure revealed a typical helicase RecA-like domain linked to a small N-terminal alpha/beta domain that likely binds the nucleic acid substrate.

"Now that we know the exact structure of the part of UvsW that interacts with DNA, we can take a closer look at how this important enzyme works,” explained senior author Dr. Stephen White, chairman of the department of structural biology at St. Jude Children's Research Hospital. "Stable replication keeps the DNA stable, even while it is undergoing recombination. UvsW plays a major role in keeping DNA stable.”




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