August 14, 1998
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Editor: Bill Noxon
Contents of this News Tip:
Although it doesn't get the same kind of attention as its relative
(DNA), RNA is the real workhorse of the gene world. Known for its duties
as messenger, transcriber, translator and enzyme, RNA has recently been
found performing escort duty to DNA molecules.
National Science Foundation (NSF)-funded researcher Peixuan Guo of
Purdue University has observed packaging RNA, or "pRNA," in this new role
during his study of the virus known as bacteriophage Phi 29. The findings
are published in a recent issue of the journal Molecular
Cell.
Bacteriophages are viruses that infect bacteria, and they may use DNA
or RNA as genetic material. After they enter a bacterial cell, bacteriophages
take over the cell's machinery to make new copies of their own genetic
material and protective protein shell, or "capsid". What has puzzled scientists
is that bacteriophages make new capsids first, then somehow insert the
replicated copies of their genes into the capsid.
Guo found that, in the case of Phi 29 (a DNA virus), six pRNA molecules
could form hexagon shaped rings that drive viral DNA into the capsid.
The RNA hexagon attaches itself to the viral capsid and then turns like
a wrench on a bolt, which forces the DNA through the pRNA molecule and
into the capsid. Although pRNA has been found in other kinds of bacteriophages,
Guo's study is the first to show pRNA performing this particular feat.
[Greg Lester]
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NSF's Industry/University Cooperative Research Centers (IUCRC) received
an award from the Technology Transfer Society at its annual conference
July 28 in Chicago.
The Justin Morrill Award is given to organizations that establish high
standards for technology transfer activities, make significant contributions
to society and promote positive practices that influence
public policy.
NSF's $4-million annual IUCRC program in the Directorate of Engineering
has resulted in a return of $75 million in research investments by member
firms and other sponsors, according to one of the Morrill Award nomination
summaries.
More than 75 percent of industry's support to university R&D; comes
through industry-university centers, such as IUCRCs. The IUCRC program
was developed in the early 1970s. [Bill Noxon]
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Using powerful supercomputers, NSF-supported researchers have unlocked
the mystery surrounding one of the fastest, most efficient enzymes in
the human body. Acetylcholinesterase (AChE) works to instantly stop transmissions
from one nerve cell to the next nerve or
muscle cell.
AChE catalyzes the chemical reaction that breaks up acetylcholine (ACh),
a neurotransmitter, thereby serving as the off-switch for the transmission.
The speed of this process has puzzled researchers since the structure
of AChE was first modeled in 1991. The active site, where the reaction
takes place, was found deep inside a groove on AChE -- a groove too narrow
to admit ACh quickly.
Using large-scale computer simulations run at the San Diego Supercomputer
Center, Andrew McCammon of the University of California, San Diego has
shown how AChE does its job: by "breathing". The simulations show that
this flexing motion causes AChE to inhale and exhale ACh molecules almost
as fast as if the groove was always open. Why, then, is the channel blocked
at all?
McCammon's research has demonstrated that this motion keeps larger
molecules out of the space intended for ACh. This finding shows that enzymes
can use movements to select particular substrates in crowded environments
like the inside of a living organism. This work, first published in the
August 4 issue of the Proceedings of the National
Academy of Sciences, also demonstrates the power of using computer simulations
to gain insight on major biological problems. [Greg
Lester]
For more information on AChE, see: http://chemcca10.ucsd.edu/ache_animated.html
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