News: A simple fusion to jump-start evolution

A simple fusion to jump-start evolution
December 18th, 2008 in General Science / Biology


With the aid of a straightforward experiment, researchers have provided some
clues to one of biology's most complex questions: how ancient organic
molecules came together to form the basis of life.

Specifically, this study, appearing online this week in JBC, demonstrated
how ancient RNA joined together to reach a biologically relevant length.

RNA, the single-stranded precursor to DNA, normally expands one nucleic base
at a time, growing sequentially like a linked chain. The problem is that in
the primordial world RNA molecules didn't have enzymes to catalyze this
reaction, and while RNA growth can proceed naturally, the rate would be so
slow the RNA could never get more than a few pieces long (for as nucleic
bases attach to one end, they can also drop off the other).

Ernesto Di Mauro and colleagues examined if there was some mechanism to
overcome this thermodynamic barrier, by incubating short RNA fragments in
water of different temperatures and pH.

They found that under favorable conditions (acidic environment and
temperature lower than 70 C), pieces ranging from 10-24 in length could
naturally fuse into larger fragments, generally within 14 hours.

The RNA fragments came together as double-stranded structures then joined at
the ends. The fragments did not have to be the same size, but the efficiency
of the reactions was dependent on fragment size (larger is better, though
efficiency drops again after reaching around 100) and the similarity of the
fragment sequences.

The researchers note that this spontaneous fusing, or ligation, would a
simple way for RNA to overcome initial barriers to growth and reach a
biologically important size; at around 100 bases long, RNA molecules can
begin to fold into functional, 3D shapes.

Article link: http://www.jbc.org/cgi/content/abstract/M805333200v1

Source: American Society for Biochemistry and Molecular Biology
http://www.physorg.com/news148844248.html

Posted by
Robert Karl Stonjek


.

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