Enterobacteria phage M13
| M13 bacteriophage | |
|---|---|
 |
|
| Blue: Coat Protein pIII; Brown: Coat Proteín pVI; Red: Coat Protein pVII; Limegreen: Coat Protein pVIII; Fuchsia: Coat Proteín pIX; Purple: Single Stranded DNA | |
| Virus classification | |
| Group: | Group II (ssDNA) |
| Family: | Inoviridae |
| Genus: | Inovirus |
| Species | |
M13 is a virus that infects the bacterium Escherichia coli. It is composed of a circular single-stranded DNA molecule encased in a thin flexible tube made up of about 2700 copies of a single protein called P8, the major coat protein. The ends of the tube are capped with minor coat proteins. Infection starts when the minor coat protein P3 attaches to the receptor at the tip of the F pilus of the bacterium. Infection with M13 is not lethal; however, the infection causes turbid plaques in E. coli because infected bacteria grow more slowly than the surrounding uninfected bacteria. It engages in a viral lifestyle known as a chronic infection which is neither lytic or temperate. However a decrease in the rate of cell growth is seen in the infected cells. M13 plasmids are used for many recombinant DNA processes, and the virus has also been studied for its uses in nanostructures and nanotechnology.
The phage coat is primarily assembled from a 50 amino acid protein called pVIII (or p8), which is encoded by gene VIII (or g8) in the phage genome. For a wild type M13 particle, it takes approximately 2700 copies of p8 to make the coat about 900 nm long. The coat's dimensions are flexible though and the number of p8 copies adjusts to accommodate the size of the single stranded genome it packages. For example, when the phage genome was mutated to reduce its number of DNA bases (from 6.4 knt to 221 nt), then the number of p8 copies was decreased to fewer than 100, causing the p8 coat to shrink in order to fit the reduced genome. The phage appear to be limited at approximately twice the natural DNA content. However, deletion of a phage protein (p3) prevents full escape from the host E. coli, and phage that are 10-20X the normal length with several copies of the phage genome can be seen shedding from the E. coli host.
...
Wikipedia