Why 5'->3' and not 3'->5' ?

Adam Noel Harris adhar at stanford.edu.XX
Fri Mar 27 21:12:55 EST 1998

Scott McMahan <mcmahan at oncology.wisc.edu> wrote:
:In article <slrn6hm0r0.b70.adhar at elaine44.Stanford.EDU>,
:adhar at stanford.edu.XX (Adam Noel Harris) wrote:
::Yes, but why is the triphosphate group not off the 3' end? :)
:I wish I knew.  I'm sure it is somewhat related to the fact that chemistry
:is not random, but I can't say why it would be favored off the 5' end and
:not the 3' end.  Does anyone know?

I don't know (oh yeah, I asked the smart-ass question), but I'd argue that
it need not be favored.  Look at cAMP, where the phosphate bonds with
_both_ carbons.  Perhaps it's just an L- vs. D- amino acid thing, where it
could have happened either way, but once it was decided, nucleic acid
building was locked in to the 5'->3' mode.

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