The goal of the work reported here is to understand the precise molecular mechanism of the process of DNA packaging in dsDNA bacteriophages. Cryo-EM was used to directly visualize the architecture of the DNA inside the capsid and thus to measure fundamental physical parameters such as inter-strand distances, local curvatures, and the degree of order. We obtained cryo-EM images of bacteriophage that had packaged defined fragments of the genome as well as particles that had partially completed the packaging process. The resulting comparison of structures observed at intermediate and final stages shows that there is no unique, deterministic DNA packaging pathway. Monte Carlo simulations of the packaging process provide insights on the forces involved and the resultant structures.
Bibliographical noteFunding Information:
This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy, also under Contract No. DE-AC02-05CH11231. Support was also provided via NIH grants # DE03606 (DLA) and GM051487 (CB).
- Bacteriophage structure
- Cryo-electron microscopy
- DNA packaging
- Monte Carlo