New structure solved for hyperthermophilic DNA virus

A new Science paper is out from IPD faculty Dr. Frank DiMaio titled A virus that infects a hyperthermophile encapsidates A-form DNA. Read the abstract below and the article at the link:

Extremophiles, microorganisms thriving in extreme environmental conditions, must have proteins and nucleic acids that are stable at extremes of temperature and pH. The nonenveloped, rod-shaped virus SIRV2 (Sulfolobus islandicus rod-shaped virus 2) infects the hyperthermophilic acidophile Sulfolobus islandicus, which lives at 80°C and pH 3. We have used cryo–electron microscopy to generate a three-dimensional reconstruction of the SIRV2 virion at ~4 angstrom resolution, which revealed a previously unknown form of virion organization. Although almost half of the capsid protein is unstructured in solution, this unstructured region folds in the virion into a single extended a helix that wraps around the DNA. The DNA is entirely in the A-form, which suggests a common mechanism with bacterial spores for protecting DNA in the most adverse environments.

The SIRV2 protein dimer helices fully encapsulate the DNA. (A) Three asymmetric units of the virion are shown, illustrating how the N-terminal helices wrap around the DNA, forming antiparallel helix-helix packing. (B) Side view. (C) Surface view of the protein (using a 1.4 Å probe radius). (D) The right-handed solenoidal supercoiling of the DNA, with three turns shown.