Re: Life in the Lab -- Fox and the Nobel Prize
Sun, 16 May 1999 02:12:33 EDT

In a message dated 5/14/99 5:38:32 AM Mountain Daylight Time, writes:

> Where did Fox demonstrate the use of polynucleotides
> (DNA? RNA? something else?) as templates for protein synthesis?

See _Molecular Evolution and the Origin of Life_, Revised Edition, by Sidney
W. Fox and Klaus Dose (Marcel Dekker inc., New York, 1977), pages 232-237,
254 for details. Basically he describes various experiments, including one
in which microspheres made up of lysine-rich proteinoids and
homopolynucleotides selectively polymerized those amino acids with
homocodons. In other words, microspheres containing poly(A)nucleotides
selectively polymerized lysine (whose codon is AAA), those containing
poly(C)nucleotides selectively polymerized proline (CCC), those containing
poly(G)nucleotides selectively polymerized glycine (GGG) and those containing
poly(U)nucleotides selectively polymerized phenylalanine (UUU).

> I thought
> in all his experiments where replication occurred, the proteins were the
> templates.

This is a common misconception; however, he does make it clear that in
proteinoid microspheres it is the proteins that carry the information needed
to replicate functional macromolecules.

> > ...From there it is simply
> > a matter of selection to coaxe protocells into producing a system in
> > which catalytic activity and information storage are divided between two
> > different types of macromolecules (proteins and DNA/RNA, respectively)...
> Don't you already have this above?

Not quite. For one thing, polynucleotides formed abiotically have a
different structure from that of nucleic acids, though they have similar
functions. For another, while the synthesis mechanism is in place, at the
time Fox wrote the above book with Dose there was no evidence that the
polymerized amino acids had any function. At that stage of abiotic evolution
the proteinoids were still the only molecules that contained the necessary
information to replicate functional polypeptides. However, this was because
the lab experiments were based on *homo*polynucleotides.
Heteropolynucleotides would (from the results presented in Fox's book)
presumably polymerize functional polypeptides; however, so far as I know no
one has demonstrated how to make a nonrandom polynucleotide abiotically that
would code for a functional polypeptide. As such, heteropolynucleotides
capable of coding for functional polypeptides would have had to have been
made by microspheres using polypeptides as templates, something which has
been experimentally demonstrated. Furthermore, just as the polynucleotides
show selectivity for certain amino acids, so too do polypeptides show
selectivity for specific sequences of nucleotides. As such, there is strong
experimental support for the idea that nonrandom heteropolynucleotides
capable of coding for functional polynucleotides were made using proteinoids
as templates and later, when incorporated into nucleoprotein microspheres,
started synthesizing functional polypeptides. From there, it was only a
matter of time until modern catalytic proteins and modern informational
nucleic acids evolved.

Kevin L. O'Brien