Once inside a cell, the virus manipulates the cell's machinery to produce all the necessary components, including genetic material, to assemble new viruses. It is here that the biological motor is needed to fill newly assembled envelopes with their genetic material, Rossmann says. The new viruses are then released from the host cell and are free to infect other cells. The study also will provide scientists with new insights on how molecular motors work in biology, says Dwight Anderson, professor at the University of Minnesota. Working in a micro-droplet, or an area the size of a very small drop, the motor packages a DNA about 130 times longer than the viral shell, in just three minutes.
Bacteriophages are viruses that only infect bacteria.
They are widely used in laboratory research because they are often similar in structure to human viruses. Phi29 infects a type of bacteria known as Bacillus subtilis. Five identical enzymes, called ATPases, are positioned around the connector, just outside the opening in the virus shell. The enzymes break down the cell's chemical fuel, called ATP, to produce the energy needed to power the motor. The researchers postulate that successive chemical reactions produced by the ATP cause the phi29 connector to oscillate and rotate, pulling the DNA into the shell two base pairs at a time.