News: Surprising Details Of Evolution Of Protein Translation Revealed
- From: "Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx>
- Date: Mon, 18 Aug 2008 13:07:08 -0400 (EDT)
Surprising Details Of Evolution Of Protein Translation Revealed
ScienceDaily (Aug. 17, 2008) - A new study of transfer RNA, a molecule that
delivers amino acids to the protein-building machinery of the cell,
challenges long-held ideas about the evolutionary history of protein
synthesis.
In the study, researchers report that the dual functions of transfer RNA
(reading the genetic blueprint for a protein, and adding a specific amino
acid to the protein as it is formed) appear to have originated independently
of one another.
University of Illinois crop sciences professor Gustavo Caetano-Anollés and
postdoctoral researcher Feng-Jie Sun made the discovery by looking for clues
to the evolution of protein translation in the sequence and structure of
transfer RNA (tRNA).
"Structure is highly conserved, capturing information that is evolutionarily
deep," Caetano-Anollés said. "It was only logical to focus on transfer RNA,
a molecule that is believed to be very ancient and is truly central to the
entire protein synthesis machinery." During protein synthesis, tRNA's dual
function is reflected in its unique
L-shaped structure. One end of the molecule decodes messenger RNA (a
molecule that carries instructions for the sequence of amino acids in a
protein), while the other transfers a specific amino acid to the growing
protein chain.
In previous studies, scientist assumed that the two functional domains of
tRNA had evolved together. Sun and Caetano-Anollés put this assumption to
the test.
They began by constructing an evolutionary family tree based on the sequence
and two-dimensional structures of tRNA molecules representing every domain
of life (bacteria; the microbes known as archaea; and eucarya, the domain
that includes animals, plants, fungi and many other organisms) as well as
viruses.
There are several dozen tRNAs (each reads a specific region of the genetic
blueprint for a protein and each carries only one of the 20-plus amino acids
found in proteins) so the researchers looked for clues to their evolutionary
histories by comparing their physical and functional traits.
They converted the unique features of the individual tRNA cloverleaf
structures into coded characters, a process that allowed a computerized
search for the most parsimonious (the simplest, most probable) tRNA family
trees for different organismal lineages. In this way they were able to test
competing evolutionary hypotheses against the data mined from the structure
of the tRNA itself.
"Our findings uniquely focus on structure, the actual aspect of the molecule
that encases its function," Caetano-Anollés said.
The analysis indicated that the two functions of the tRNA had different
evolutionary histories, Sun said, which suggests that they were acquired at
different points in time.
The study predicted that the loading of amino acids on tRNA molecules
preceded the refinement of the genetic code into codons, the regions on the
messenger RNA that are read by individual tRNAs.
"For the first time, we believe we make this distinction between the
evolution of the genetic code (codon discovery) and the evolution of amino
acid charging," Sun said.
The new findings are detailed in the July 30 Public Library of Science
(PLoS) ONE.
Adapted from materials provided by University of Illinois at
Urbana-Champaign.
University of Illinois at Urbana-Champaign (2008, August 17). Surprising
Details Of Evolution Of Protein Translation Revealed. ScienceDaily.
Retrieved August 18, 2008, from
http://www.sciencedaily.com/releases/2008/08/080812135517.htm
Posted by
Robert Karl Stonjek
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