Concerning the origin of life,
I don't think it is a coincidence that tRNA's
3' acceptor end, end in a stem coded CCA, and the
main currency of energy is ATP, and an
ATP is used to activate amino acids for
incorporation into proteins. Note all the 'A's.

"The enzyme aminoacyl-tRNA synthetase
recognizes both a particular amino acid and 
the tRNA carrying the corresponding anticodon. 
This synthetase cataylzes the
formation of an aminoacyl tRNA, 
with accompanying hydrolysis of one ATP"    
- Bio,  Mathews, van Holde.

There wasn't always an enzyme to do this.
What then was its precursor? 

I tend to think we have clues in the acceptor stem
that always ends in A (AMP) coupled with the fact
that an ATP  is needed to link amino acids.

It seems likely that that A at the end of the acceptor
stem was originally an ATP and that was the link
between the RNA world and proteins OR the link
between the tRNA ( basically a bit of folded RNA)
and proteins ( linked amino acids)

This might also suggest why ATP became the main
energy currency. Either that, or the other way around,
perhaps this is why the acceptor stem ends in A
(preceded by CC which could remain unpaired due to
a pyrimidine dimer - see other posts)

Also note that in past posts I have stressed the 
importance of purines - even to the point of
suggesting a purine world before the RNA world idea.
Note that the main energy currency is mostly the
purine based ATP, but also used is the other purine
based GTP.

"The purine nucleotides have a wide range of uses while
the pyrimidines act more as handles than anything else"
Molecular Bio of the Cell, - Albers.

What do others think of my idea of the A on the acceptor
stem somehow related to the A of ATP the energy currency
of life?

Tom Hendricks
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