WEST LAFAYETTE, Ind. - Researchers have discovered the atomic structure of a powerful "molecular motor" that packages DNA into the head segment of some viruses during their assembly, an essential step in their ability to multiply and infect new host organisms.
The researchers, from Purdue University and The Catholic University of America, also have proposed a mechanism for how the motor works. Parts of the motor move in sequence like the pistons in a car's engine, progressively drawing the genetic material into the virus's head, or capsid, said Michael Rossmann, Purdue's Hanley Distinguished Professor of Biological Sciences.
The motor is needed to insert DNA into the capsid of the T4 virus, which is called a bacteriophage because it infects bacteria. The same kind of motor, however, also is likely present in other viruses, including the human herpes virus.
"Molecular motors in double-stranded DNA viruses have never been shown in such detail before," said Siyang Sun, a postdoctoral research associate working in Rossmann's lab.
Findings are detailed in a paper appearing online on Dec. 24 in the journal Cell. The lead authors are Sun and Kiran Kondabagil, a research assistant professor at Catholic University of America working with biology professor Venigalla B. Rao.
"This research is allowing us to examine the inner workings of a virus packaging motor at the atomic level," Rao said. "This particular motor is very fast and powerful."
Other researchers have determined that the T4 molecular motor is the strongest yet discovered in viruses and proportionately twice as powerful as an automotive engine. The motors generate 20 times the force produced by the protein myosin, one of the two proteins responsible for the contraction and strength of muscles.
The virus consists of a head and tail portion. The DNA-packaging motor is located in the same place where the tail eventually connects to the head.
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