(A) Electron density maps. Upper panel: Alanine introduced by the GCU codon in the universal genetic code. Lower panel: Alanine introduced by the UGG codon in the simplified code. (B) Activity of proteins synthesized by the simplified and universal codes from the gene for each code.

Copyright : Tokyo Institute of Technology

PRESS RELEASE

Source: Tokyo Institute of Technology, Center for Public
Information

For immediate release: 24 August 2012

Tokyo Institute of Technology research: Simplifying genetic codes
to look back in time

(Tokyo, 24 August 2012) Tokyo Institute of Technology researchers
show simpler versions of the universal genetic code can still
function in protein synthesis

Daisuke Kiga and co-workers at the Department of Computational
Intelligence and Systems Science at Tokyo Institute of Technology,
together with researchers across Japan, have shown that simpler
versions of the universal genetic code, created by knocking out
certain amino acids, can still function efficiently and accurately
in protein synthesis [1]. The researchers conducted experiments
altering the genetic codein a test tube. They removed the amino
acid tryptophan and discovered that the resulting simplified code
could still generate proteins as before. By knocking out individual
amino acids and observing the effects, scientists will be able to
understand how early primordial organisms may have functioned and
evolved. There will be also numerous applications for simplified
genetic strains in laboratory experiments, which could potentially
prevent non-natural genetically modified materials from entering
the natural world.

Details: Background, significance, and future developments

Daisuke Kiga and co-workers of the Department of Computational
Intelligence and Systems Science at Tokyo Institute of Technology,
together with researchers across Japan, have shown that simpler
versions of the universal genetic code – created by knocking out
certain amino acids – can still function efficiently and accurately
in protein synthesis. The researchers conducted cell-free
experiments altering the genetic code.

All current life forms on Earth have 20 amino acids in their
genetic code. However, scientists believe that this was not always
the case, and that organisms evolved from simpler genetic codes
with fewer amino acids. Amino acids are linked in accordance with
codons – a 3-letter combination of the four base nucleotides
(G, A, T and C) in a genetic code. There are 64 possible codons,
and so most amino acids are produced by several different codons,
except for tryptophan and methionine, which are generated by just
one codon each. Tryptophan is thought to be the most recent amino
acid to become part of the universal genetic code.

Kiga and his team took the codon for tryptophan, and reassigned it
to code for the amino acid alanine instead. They discovered the
resulting simplified code could still generate proteins as before.
The researchers also reassigned another codon originally for the
amino acid cysteine and replaced it with serine. This simplified
code without cysteine was able to synthesise an active
enzyme.

By knocking out individual amino acids and observing the effects,
scientists will be able to understand how early primordial
organisms may have functioned and evolved. There are also numerous
applications for simplified genetic codes in laboratory experiments
and clinical trials.

Before emergence of the current universal genetic code, primitive
organisms that may have used only 19 amino acids could benefit from
horizontal gene transfer, where cells transfer genetic material
between one another. This is a key method used by bacteria to
develop resistance to drugs. An organism with the current universal
genetic code for 20 amino acids would have competitive advantages
in its ability to synthesise proteins, but could not engage in
genetic transfer with the rest of the population. Only when a
suitably large gene pool of organisms with 20 amino acids is
available could horizontal transfer occur between these life forms
and they could then thrive. This implies that organisms with a
simpler genetic code could be used as a barrier in laboratory
experiments, preventing new genetically modified strains from
escaping to the natural world.

Further information:

Yukiko Tokida

Center for Public Information, Tokyo Institute of Technology

2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan

E-mail: kouhou@jim.titech.ac.jp

URL: http://www.titech.ac.jp/english/

Tel: +81-3-5734-2975

Fax: +81-3-5734-3661

About Tokyo Institute of Technology

As one of Japan’s top universities, Tokyo Institute of
Technology seeks to contribute to civilization, peace and
prosperity in the world, and aims at developing global human
capabilities par excellence through pioneering research and
education in science and technology, including industrial and
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educating highly moral students to acquire not only scientific
expertise but also expertise in the liberal arts, and a balanced
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researching deeply from basics to practice with academic mastery.
Through these activities, we wish to contribute to global
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Website: http://www.titech.ac.jp/english/