The crystal structure of a molecule from a primitive fungus
has served as a time machine to show researchers more about the
evolution of life from the simple to the complex.
 | | he crystal structure of a molecule from a primitive fungus has served as a time machine to show researchers more about the evolution of life from the simple to the complex. |
By studying the three-dimensional version of the fungus
protein bound to an RNA molecule, scientists from Purdue
University and the University of Texas at Austin have been
able to visualize how life progressed from an early self-replicating
molecule that also performed chemical reactions to one in which
proteins assumed some of the work.
"Now we can see how RNA progressed to share functions with
proteins," said Alan Lambowitz, director of the University of Texas
Institute for Cellular and Molecular Biology. "This was a critical
missing step."
Results of the study were published in Thursday's (Jan. 3)
issue of the journal Nature.
"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.
Posted 3rd January 2008
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