Re: Ribosome origin explained?

"William L Hunt" <wlhunt@xxxxxxxxxxxxx> wrote in message news:goenhl$17i8$1@xxxxxxxxxxxxxxxxxxxxxx
On Tue, 24 Feb 2009 12:34:18 -0500 (EST), "Perplexed in Peoria"
<jimmenegay@xxxxxxxxxxxxx> wrote:

If this is correct, it is the most important discovery regarding the
origin of life since - well ... - since the origin of life.

http://blogs.sciencemag.org/origins/2009/02/deconstructing-the-ribosome.html


I wouldn't get excited about this just yet. If they can derive the
initial small core functional unit and show that it can function by
itself and what it does, that would be somehting. I like their
approach very much though.
But I'm uncomfortable with the feeling there must be non-darwinian
processes involved to explain even the ribosome evolution. It seems
almost everyone other than myself thinks the evolution of the genetic
code must involve something more than standard darwinian natural
selection.
I remember a long time ago we had a long discussion on the evolution
of the ribosome with both of us feeling the ribosome first evolved for
some other function than making polypeptides. I don't know if your
views have changed but mine have changed completely (and before this
article). I now think it evolved from a very simple beginning but
making polypeptides from the very beginning.

You are right that I thought that at least parts of the ribosome had
another function. And it looks (from this paper) that I may need to
modify that belief.

I also have never thought there ever was a takeover event of another
kind either. This is when someone thinks polypeptides (the genetic
code) were first made on minerals or by tRNAs alone or some other way
and then waves their hands and says and then the ribosome took over.
So I think when we have an explanation of how the ribosome evolved,
we will also have an explanation of how the genetic code evolved. The
two will turn out to be one and the same.

I don't believe in that kind of 'takeover' either. And I'm quite sure that
the code and the ribosome evolved during the same era. But I don't see
that the ribosome really tells us much about the code (other than its
triplet nature, and the 'wobble' thing). The code is implemented in the
tRNAs and aaRSs. With a mystery as to how the tRNAs were recharged
with amino acids back before there were any aaRSs.

However, I would say that an explanation of how the ribosome evolved
will tell us a lot about how tRNA evolved. The primordial tRNA may
have consisted of the acceptor stem and D loop, with the anticodon
stem and T loop added later.

It may be difficult but it should be more straightforward to work
out the evolution of the complex but real structure of the ribosome
rather than trying to just expain the evolution of an abstract concept
of an encoding scheme (the genetic code).

I agree. But don't neglect the possibility that as the ribosome grew by
accretion, some of those segments added may have come from some
other structure with some other function. From what I have read so
far, the concept of punctuated equilibrium may apply here too.

.

Relevant Pages

  • Re: Ribosome origin explained?
    ... origin of life since - well ... ... processes involved to explain even the ribosome evolution. ... some other function than making polypeptides. ...
    (sci.bio.evolution)
  • News: Molecular sleuths track evolution through the ribosome
    ... Molecular sleuths track evolution through the ribosome ... A new study of the ribosome, the cell's protein-building machinery, sheds ... each made up of RNA and proteins. ...
    (sci.bio.evolution)
  • Re: Life?
    ... the cell is a unit of life. ... And ribosome and Golgi apparatus can't be ...
    (sci.bio.misc)