NSF PR 00-92 - December 6, 2000
This material is available primarily for archival
purposes. Telephone numbers or other contact information
may be out of date; please see current contact information
DNA "Motors" Are Key to Virus Replication
A crossection through the DNA motor showing
the individual protein molecules and DNA
A model for the function of the DNA-spooling
function of the motor.
Detailed structure of the DNA motor (a) top
view (b) side view (c) individual protein
to QuickTime movie
of DNA Packaging Motor
One of nature's smallest motors helps viruses package
their genetic material, according to research described
in the December 7 issue of the scientific journal
Scientists at Purdue University and the University
of Minnesota have solved the three-dimensional structure
of the central component of a biological motor that
powers the DNA packaging system in a virus, providing
scientists with their first glimpse of such a motor
system. The study revealed how the core of a tiny
motor, just millionths of a millimeter in size, is
constructed and suggests how it works to pack long
stretches of the virus' genetic material into its
outer shell during the process of viral replication.
The work was made possible in part by the National
Science Foundation (NSF), through its Molecular Biophysics
program. The results point to new opportunities in
nanoscience, according to NSF program director Parag
Chitnis. "One application of this work will be in
developing drugs that would inhibit virus replication.
Many viruses that infect humans, such as Herpes, use
a similar machinery for DNA packaging," he said.
The project may provide clues as to how DNA is packaged
in similar viruses - including Herpes virus, which
causes human ailments such as Herpes simplex, chicken
pox and shingles - and suggest ways for developing
drugs that prevent illnesses caused by viral pathogens.
"This study provides the first knowledge of a DNA packaging
motor," said Michael Rossmann, Hanley Distinguished
Professor of Biological Sciences at Purdue. "Though
other motor systems have been studied in biology,
this is the first motor known to translocate genetic
Viruses are essentially a simple parasite consisting
only of an envelope that contains the genetic material
ready for transportation from one host to another.
They can reproduce only after infecting a host cell.
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 said. The new viruses are then
released from the host cell and are free to infect
The study also will provide scientists with new insights
on how molecular motors work in biology, said Dwight
Anderson, professor at the University of Minnesota.
"The beauty of phi29 motor is that it provides a relatively
simple system to investigate the mechanism of DNA
packaging," Anderson said. "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.
In the study, Rossmann, along with Purdue researcher
Timothy Baker and others at Purdue, and Anderson and
his co- workers at Minnesota, used micro-imaging techniques
-- including X-ray crystallography and cryo-electron
microscopy -- to determine the structure of the DNA
packaging motor in a virus called Bacteriophage phi29.
Bacteriophages are viruses that only infect bacteria.
They are widely used in laboratory research because
they are often similar in structure to human viruses.
The research was also funded by the National Institutes
of Health and Purdue University.
for QuickTime movie of DNA packaging motor.