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Science Forum Index » Bio Evolution Forum » News: History Of Life Seen In The Structure Of Transfer RNA
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| Robert Karl Stonjek |
 Posted: Mon Mar 10, 2008 7:48 pm |
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History Of Life Seen In The Structure Of Transfer RNA
ScienceDaily (Mar. 10, 2008) - Transfer RNA is an ancient molecule, central
to every task a cell performs and thus essential to all life. A new study
from the University of Illinois indicates that it is also a great historian,
preserving some of the earliest and most profound events of the evolutionary
past in its structure.
The study, co-written by Gustavo Caetano-Anollés,* a professor of crop
sciences, and postdoctoral researcher Feng-Jie Sun, appears March 7 in PLoS
Computational Biology.
Of the thousands of RNAs so far identified, transfer RNA (tRNA) is the most
direct intermediary between genes and proteins. Like many other RNAs
(ribonucleic acids), tRNA aids in translating genes into the chains of amino
acids that make up proteins. With the help of a highly targeted enzyme, each
tRNA molecule recognizes and latches onto a specific amino acid, which it
carries into the protein-building machinery. In order to successfully add
its amino acid to the end of a growing protein, tRNA must also accurately
read a coded segment of messenger RNA, which gives instructions for the
exact sequence of amino acids in the protein.
The fact that tRNA is so central to the task of building proteins probably
means that it has been around for a long time, Caetano-Anollés said. His
inquiry began with a hunch that understanding the structural properties of
tRNA would shed light on how organisms and viruses evolved.
"Perhaps in evolution there are things that are so fundamental that they are
kept, held onto, for millions or even billions of years," Caetano-Anollés
said. "Those are the fossils, the molecular fossils, that tell us about the
past. Therefore, studying these molecules can address fundamental questions
in biology and evolution."
All tRNAs assemble themselves into a shape that, if flattened, resembles a
cloverleaf. The team began by looking for patterns in this cloverleaf
structure, using detailed data from hundreds of molecules representing
viruses and each of the three superkingdoms of life: archaea, bacteria and
eukarya.
The researchers converted all distinguishing features of the individual tRNA
cloverleaf structures into coded characters, a process that allowed a
computerized search for the most "parsimonious" (that is, the simplest, most
probable) tRNA family tree. They conducted the same analysis on the tRNAs of
each of the superkingdoms, to see how far these groupings diverged from the
overall tree. This comparison allowed them to determine the order in which
viruses and each of the superkingdoms diverged.
The new analysis supports an earlier study that suggested that the archaea
were the first to arise as an evolutionarily distinguishable group. Archaea
are microbes that can survive in boiling acid, near sulfurous ocean vents or
in other extreme environments. The earlier study, also led by
Caetano-Anollés, analyzed the vast catalog of protein folds -- those
precisely configured regions in proteins that give them their
functionality -- as a guidebook to evolutionary history.
"The transfer RNA data matches our earlier data," Caetano-Anollés said.
"This is important because two lines of independent evidence are supporting
each other."
The new analysis also indicates that viruses emerged not long after the
archaea, with the superkingdoms eukarya and bacteria following much later --
and in that order. This finding may influence the ongoing debate over
whether viruses existed prior to, or after, the emergence of living cells,
Caetano-Anollés said.
"This supports the idea that viruses arose from the cellular domain," he
said.
*Caetano-Anollés is an affiliate of the U. of I. Institute for Genomic
Biology.
Adapted from materials provided by University of Illinois at
Urbana-Champaign, via EurekAlert!, a service of AAAS.
University of Illinois at Urbana-Champaign (2008, March 10). History Of Life
Seen In The Structure Of Transfer RNA. ScienceDaily. Retrieved March 10,
2008, from http://www.sciencedaily.com/releases/2008/03/080306202749.htm
Posted by
Robert Karl Stonjek |
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