The mechanism by which dsDNA is packaged into tailed bacteriophage virions has fascinated molecular biologists since it was realized, over four decades ago, that these structures contain long dsDNA molecules that are hundreds of times more compact than dsDNA in solution. Experiments in the 1970s showed that, rather than condensing the DNA first and then assembling a shell around this DNA core, tailed-phage DNA is inserted into a preformed protein container (called a prohead or procapsid). Mmolecular genetics studies indicate that the basic machinery of dsDNA packaging is similar in all tailed phages.
The recent burst of structural progress concerning phage DNA-packaging proteins, as well as the introduction of optical tweezer technology into this field, has allowed the formulation of much more detailed ideas for the mechanism by which the DNA-packaging motor pumps DNA into phage procapsids. Potential applications of packaging nanomotors in nanotechnology and biology are beginning to be described, for example these nanomotors could be used for efficient delivery of nucleic acids or related molecules across barriers such as cell membranes or for applications in single-molecule DNA sequencing. There is little doubt that this will be a fertile research area for some time into the future.
The DNA-packaging nanomotor of tailed bacteriophages. 2011 Nat Rev Microbiol. 9(9):647-57 doi: 10.1038/nrmicro2632
Tailed bacteriophages use nanomotors, or molecular machines that convert chemical energy into physical movement of molecules, to insert their double-stranded DNA genomes into virus particles. These viral nanomotors are powered by ATP hydrolysis and pump the DNA into a preformed protein container called a procapsid. As a result, the virions contain very highly compacted chromosomes. Here, I review recent progress in obtaining structural information for virions, procapsids and the individual motor protein components, and discuss single-molecule in vitro packaging reactions, which have yielded important new information about the mechanism by which these powerful molecular machines translocate DNA.