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The crystal
structure of an RNA molecule bound to a protein was used by Purdue
and University of Texas at Austin researchers to study a stage of
evolution.
Image courtesy of
Barbara Golden, Purdue University Department of Biochemistry |
"It's thought that RNA, or a molecule like it,
may have been among the first molecules of life, both carrying genetic
code that can be transmitted from generation to generation and folding
into structures so these molecules could work inside cells," said
Purdue structural biologist Barbara Golden. "At some point, RNA
evolved and became capable of making proteins. At that point, proteins
started taking over roles that RNA played previously - acting as
catalysts and building structures in cells."
In order to show this and learn more about the evolution from RNA to
more complex life forms, Lambowitz and Paul Paukstelis, lead author
and a research scientist at the Texas institute, needed to be able to
see how the fungus' protein worked. That's where Golden's team joined
the effort and crystallized the molecule at Purdue's macromolecular
crystallization facility.
"Obviously, we can't see the process of moving from RNA to RNA and
proteins and then to DNA, without a time machine," Golden said. "But
by using this fungus protein, we can see this process occurring in
modern life."
Looking at the crystal, the scientists saw two things, Golden said.
One was that this protein uses two completely different molecular
surfaces to perform its two roles. The second is that the protein
seems to perform the same job that RNA performed in other simple
organisms.
"The crystal structure provides a snapshot of how, during evolution,
protein molecules came to assist RNA molecules in their biological
functions and ultimately assumed roles previously played by RNA,"
Golden said.
Before the crystallization, Lambowitz, Paukstelis and their research
team at The University of Texas at Austin were involved in a long-term
project to study the function of the basic cellular workhorse protein
and other evolutionary fossils from the fungus. In earlier work, the
scientists studied a different protein that showed how biochemical
processes could progress from a world with RNA and protein to DNA.
The protein, as found in the fungus, had adapted to take over some of
the RNA molecule's chemical reaction jobs inside cells. The protein
stabilizes the RNA molecule - called an intron - so that the RNA can
cut out non-functional genetic material and splice together the ends
of a functional gene, Paukstelis said.
"The RNA molecule in our study is capable of performing a specific
chemical reaction on itself, but it requires a protein for this
reaction to take place efficiently," he said.
This basic scientific information eventually could lead to clinical
applications.
"This work has potential applications in the development of antifungal
drugs to battle potentially deadly pathogens; that's one of the next
steps," Lambowitz said. "Another is to produce more detailed
structures so that we can understand the ancient chemical reactions."
Golden and Lambowitz are senior authors of the report. Golden is a
member of the Markey Center for Structural Biology and Purdue Cancer
Center. The Markey Center will be housed in the Hockmeyer Hall of
Structural Biology when it's completed on the West Lafayette campus.
Other researchers involved in this study along with Paukstelis were
Jui-Hui Chen, a Purdue biochemistry doctoral student, and Elaine
Chase, a Purdue biochemistry research technician.
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