Masih percaya tahun 2012 ini dengan bualan orang semitik primitif yang ngibul
bilang Adam itu ciptaan allah yang tidak berbukti ada?
Ya goblok.
Ya dungu.
Ya bodoh.
Ya bodoh.
Ya pandir.
--
Web address:
http://www.sciencedaily.com/releases/2012/12/
121211193303.htm
Resurrection of Extinct Enzymes Reveals Evolutionary Strategy for the Invention
of New Functions
--
Duplication events and changes in specificity and activity in evolution of S.
cerevisiae MalS enzymes. Gene duplications occur frequently during evolution
and are important drivers of functional innovation. The MalS enzyme family in
the yeast Saccharomyces cerevisiae is a family of fungal metabolic enzymes that
all originated from the same ancestral gene through repeated duplications.
Resurrection of key ancestral enzymes allowed tracking of the changes in
activity that happened during evolution. The very first pre-duplication enzyme
was promiscuous, preferring maltose-like sugars but having trace activity for
isomaltose-like sugars. Structural analysis and activity measurements indicate
that both activities cannot be fully optimized in a single enzyme. Duplication
allowed optimization of the different functions in different copies, finally
resulting in an arsenal of specialized present-day enzymes that allow growth on
different complex sugars. Figure depicts hydrolytic activity of all seven
present-day MalS alleles as well as of key reconstructed ancestral (anc)
versions of these enzymes. The width of the colored bands corresponds to
kcat/Km of the enzyme for a specific substrate. (Credit: Chris Brown)
--
Dec. 11, 2012 How does evolution innovate? We exist because our ancestors
have had the ability to adapt successfully to changes in their environment;
however, merely examining present-day organisms can limit our understanding of
the actual evolutionary processes because the crucial events have been masked
by the passage of aeons -- what we need is a time machine. Scientists from VIB,
KU Leuven, University of Ghent and Harvard have done the next-best thing; by
reconstructing DNA and proteins from prehistoric yeast cells, they were able to
directly examine the evolutionary forces that have acted over the last 100
million years to shape modern-day enzymes -- biological catalysts that enable
organisms to manipulate molecules to their will.
The scientists set out to explore how new genes emerge, how they contribute to
the survival of the evolving organism, and how, after a humble start, evolution
then refines the function of new genes and hones the efficiency of the enzymes
that they encode. One of the richest sources of such new genes is the chance
duplication of existing genes. One copy of the gene can then continue to encode
the original enzyme, allowing it to perform its original task, while the other
is free to change and to perhaps take on a new function; alternatively, the two
new enzymes might sub-divide the original task.
Although this pattern of innovation is known to have happened many thousands of
times during evolution, the way in which it occurs hasn't been clear. In a
paper published December 11 in the online Open Access journal PLOS Biology,
Karin Voordeckers, Chris Brown and Kevin Verstrepen from VIB in Leuven,
together with Steven Maere from VIB and the University of Ghent, tackled this
problem, focusing their attention on the evolution of enzymes that have allowed
yeast to exploit changing food sources over the last 100 million years of
evolution.
The scientists 'resuscitated' ancestral yeast genes, allowing them to examine
the properties of enzymes that existed tens of millions of years ago. The
original enzyme originally enabled the yeast cells to survive on a diet of
maltose, a common sugar, but duplications of their genes gave rise to new
enzymes which opened up the possibility of feeding off other types of sugar in
the environment. The resurrection of these enzymes meant that the scientist
could build up a detailed picture of their atomic structure and directly
determine their ability to break down different types of sugars. Armed with
this information, they could work out exactly how the enzymes had changed their
specificity and how evolution drove their optimisation.
"We used sequence reconstruction algorithms to predict the DNA sequence of
ancestral genes from dozens of present-day DNA sequences. This enabled us to
rebuild the corresponding ancestral proteins and compare them with those
present today," said Steven Maere.
"We searched very specifically for how the yeast adapted to break down various
sources of sugar. We found that the primal gene that codes for the protein for
the digestion of maltose -- a sugar in grain -- was copied a number of times
during evolution. The DNA of some copies changed slightly, resulting in new
proteins that could break down different sugars. By modeling these changes in
the corresponding proteins, we now understand how just a few changes in the DNA
can lead to the development of a completely new activity in the corresponding
proteins," said Karin Voordeckers.
"New functional DNA does not appear out of thin air, but is built up gradually
from a copy of an existing segment of functional DNA. By reconstructing a piece
of prehistoric DNA that was copied several times during evolution, we were able
to investigate in detail which changes occur in each of the copies and
gradually lead to new functions. As such, our results provide a unique and
detailed view into the molecular details of Darwinian evolution" says Kevin
Verstrepen.
The scientists propose that the events observed here in the yeast cell's quest
for sugar may reflect a general strategy widely used for innovation in
evolution.
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Story Source:
The above story is reprinted from materials provided by Public Library of
Science.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal References:
Karin Voordeckers, Chris A. Brown, Kevin Vanneste, Elisa van der Zande,
Arnout Voet, Steven Maere, Kevin J. Verstrepen. Reconstruction of Ancestral
Metabolic Enzymes Reveals Molecular Mechanisms Underlying Evolutionary
Innovation through Gene Duplication. PLoS Biology, 2012; 10 (12): e1001446 DOI:
10.1371/journal.pbio.1001446
Richard Robinson. Resurrecting an Ancient Enzyme to Address Gene
Duplication. PLoS Biology, 2012; 10 (12): e1001447 DOI:
10.1371/journal.pbio.1001447
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
APA
MLA
Public Library of Science (2012, December 11). Resurrection of extinct enzymes
reveals evolutionary strategy for the invention of new functions. ScienceDaily.
Retrieved December 12, 2012, from http://www.sciencedaily.com
/releases/2012/12/121211193303.htm
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of
ScienceDaily or its staff.
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