from the biological-nanomachines dept.
According to a lengthy press release (30 January 2002), scientists at Purdue University have solved the three-dimensional structure of the bacteriophage T4 virus, which includes a complex syringe-like structure designed to inject viral DNA into a host cell. The researchers reported their work on this natural nano-mechanical device in the 31 January 2002 issue of Nature.
The study also reveals how the virus binds to the surface of the host, punctures the cell wall with a syringe-like tube and injects its own genetic blueprint into the cell. The virus uses its long-tail fibers to recognize its host and to send a signal back to the baseplate. Once the signal is received, the short-tail fibers help anchor the baseplate into the cell surface receptors. As the virus sinks down onto the surface, the baseplate undergoes a change — shifting from a hexagon to a star-shaped structure. At this time, the whole tail structure shrinks and widens, bringing the internal pin-like tube in contact with the outer membrane of the E. coli cell. As the tail tube punctures the outer and inner membranes of the E. coli cell, the virus' DNA is injected through the tail tube into the host cell. This genetic information then sets the cell's machinery to work creating replicas of the virus.
Analysis of the cell-puncturing device also reveals a structure that may hold potential for applications in nanotechnology, such as microscopic probes, said Michael Rossmann, Hanley Distinguished Professor of Biological Sciences at Purdue who directed the study. "This a very stable structure that looks like a small stylus. It might be useful as a probe in an atomic force microscope, which employs a probe of molecular dimension."
Update: Additional information on this research, including links to high-resolution images of the T4 virus and the viral baseplate mechanism and a news video, is available on the U.S. National Science Foundation (NSF) website.