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Science Forum Index » Bio Evolution Forum » tRNA origin
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| Author |
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| Tom Hendricks |
 Posted: Mon Mar 10, 2008 7:48 pm |
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Guest
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This paper
Thermosynthesis as energy source for the RNA World:
A model for the bioenergetics of the origin of life
Anthonie W.J. Muller ∗
Has a fascinating chart of the possible origin of tRNA.
I particularly found it interesting because I've long thought that
tRNA was the first RNA. Though I don't know enough to comment much on
his idea.
Here is the caption to the diagram
Fig. 6. The proposed evolution of tRNA and emergence of mRNA. (a) The
first tRNAs were minihelices that connected to amino acids and
yielded charged tRNAs. The charged tRNAs formed a protein with random
composition, a process catalyzed by an rRNA progenitor or possibly
a pF1 . (b) Using their arms positional tRNAs recognized a predecessor
and a follower, which resulted in a tRNA sequence that yielded a
small
protein sequence that was a key motif of pF1 . (c) The first tRNA of
the sequence extended to a template that bound all other motif tRNAs.
The positional tRNAs acquired anticodons that bound to codons on the
extension. (d) The extension was disconnected from the first tRNA
(arrow), and yielded a mRNA (start at 3′ end). Mutual tRNA recognition
disappeared but tRNA:mRNA recognition remained: this transition
from mutually recognizing positional tRNAs to a set of regular mRNA-
codon recognizing tRNAs constituted the emergence of the genetic
code.
(e) Mutual tRNA recognition had disappeared. (f) A ribosome particle
containing rRNA emerged that performed (1) aminoacyl transfer from
tRNAs in the sequence given by mRNA to a growing peptide chain and (2)
translocation along mRNA in the 3′ to 5′ direction.
I don't know how much you can get without the diagram, but it is
fascinating. |
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