Re: OoL - out at first base?

On Wed, 11 Dec 2024 19:14:06 +0000, Ernest Major wrote:

On 11/12/2024 07:32, Martin Harran wrote:

I have speculated before that prior to LUCA there were waves of
replacement as lineages added to their genetic codes, and the ones with
more biochemical versatility outcompeted their sister groups. For adding
cysteine to the genetic code allows the production of more stable and
presumably more effective proteins.
>

I generally agree with everything else you wrote but would caution you
regards that point on cyseine/cystine. A more interesting role would be
to have differential function intracellularly (reducing environment) and
externally. Consider rolls of proteases and other digestive enzymes
(and just as significantly, inhibitors of the same working defense)
that activate outside the cell. Biowarfare between organisms competing
for resources is of course a theme for this thread but always important.
I'd add that intracellular disulfides seem to be a secondary development
to the role these play in extracellular environments.