Re: News: Scientists find missing evolutionary link using tiny fungus
- From: eroot@xxxxxxxx
- Date: Sat, 5 Jan 2008 05:08:26 -0800 (PST)
On Jan 4, 2:41 pm, Evopeach <keaton1...@xxxxxxxxx> wrote:
On Jan 4, 9:32 am, Ye Old One <use...@xxxxxxxxx> wrote:
January 2, 2008
Scientists find missing evolutionary link using tiny fungus crystal.
http://news.uns.purdue.edu/x/2008a/080102GoldenEnzyme.html
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.
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.
Writer: Susan A. Steeves
ABSTRACT
Cocrystal Structure of a Tyrosyl-tRNA Synthetase Splicing Factor with
a Group I Intron RNA
Paul J. Paukstelis, Jui-Hui Chen, Elaine Chase, Alan M. Lambowitz*,
and Barbara L. Golden*
The RNA world hypothesis holds that during evolution structural and
functional roles played initially by RNA were assumed by proteins,
leading to the latter's domination of biological catalysis. This
progression can still be seen in modern biology, where ribozymes, such
as the ribosome and RNase P, have evolved into protein-dependent RNA
catalysts (RNPzymes). Similarly, group I introns use RNAcatalyzed
splicing reactions, but many function as RNPzymes bound to cellular
proteins that stabilize their catalytically active RNA structure1, 2.
One such protein, the Neurospora crassa mitochondrial tyrosyl-tRNA
synthetase (mt TyrRS; CYT-18), is bifunctional and both aminoacylates
mt tRNATyr and promotes the splicing of mt group I introns3. Here, we
determined a 4.5-Å cocrystal structure of the Twort orf142-I2 group I
intron ribozyme bound to splicing-active, C-terminally truncated
CYT-18. The structure shows that the group I intron binds across the
two subunits of the homodimeric protein using a new RNA-binding
surface distinct from that which binds tRNATyr. This RNA binding
surface provides an extended scaffold for the phosphodiester backbone
of the conserved catalytic core of the intron RNA, allowing the
protein to promote the splicing of a wide variety of group I introns.
Notably, the group I intron-binding surface includes three small
insertions and additional structural adaptations relative to
non-splicing bacterial TyrRSs, indicating a multi-step adaptation for
splicing function. The cocrystal structure provides insight into how
CYT-18 promotes group I intron splicing, how it evolved to have this
function, and how proteins could have incrementally replaced RNA
structures during the transition from an RNA to RNP world.
--
Bob.
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."
Halfvast conclusions from halfvast data. The naked genie RNA world
was discredited 20 years ago. Yeah just assume that simple old RNA
existed and could exist outside a cell and perform and then evolve
into a protein machine and work in cells whenever they also came
along. LOL!
"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."
So we saw an extant protein with two binding sites........whoopie!
"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
Oops! Those are called catalytic actions so the subject teaction can
proceed at a speed exceedingonce every picocentury.......is this a
joke article?
It seems that evos believe that if you wait 20 years people will
forget the conclusions reached previously............Dyson 1984, p24)
Scott, 1986,89 and Fox 1988, p 53-54 particularly Horgan 1991 p 119
"Headline nanosized birthday cake molecule shown to be template for
firefly evolution"
Boo-hoo-hoo. Now, tell us all why you think Jesus wants you to hate
science.
Eric Root
.
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