Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

Self and the Beginning of Life 49

“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity

which requires UV-irradiation). Each mineral catalyst promotes a spe-
cific panel of products. Of note is the finding that (1) acyclonucleosides
are produced from formamide by TiO 2 catalysis, (2) nucleosides (ade-
nosine and cytosine) can be phosphorylated by phosphate minerals, and
(3) oligomerization of phosphorylated adenosine can spontaneously take
place in formamide and water.^51

3.15 A Case for Peptide/Nucleotide/Mineral Interplay

Perhaps it may not be appropriate to ask “Which came first?” regarding
life’s origin. After all, RNA and proteins need not be mutually exclu-
sive. Why not visualize a scenario in which precursors of RNA and pro-
teins developed interactively in early metabolism? As I argued above, an
exclusive RNA World as a precursor for Protein World is untenable. In
modern biochemistry, almost all catalytic reactions within a cell require
three players: a protein (polypeptide), a fragment of RNA (a nucleotide
cofactor), and a metal. Why not view this three-part cooperation as how
life originated, instead of singling out the nucleotide cofactor as a “molec-
ular fossil” of an extinct RNA World? The cooperation of peptides and
oligo-nucleotides in early metabolism was suggested by Copley, Smith
and Morowitz.^52 This scheme is also reminiscent of Calvin’s idea of an
early appearance of monomeric metabolites before their parallel poly-
merization into proteins and nucleic acids.^53 de Duve also stressed that
bio-energetics should precede bio-informatics.^54 This proposal has been
bolstered by the experimental finding of Sutherland and his associates,
who showed that, from a simple “primordial soup” containing hydro-
gen cyanide and hydrogen sulfide (both ubiquitous in the universe), and
under catalysis provided by ultraviolet light and copper, a list of precur-
sors of the three main types of biomolecules — RNA, amino acids, and
lipids — can be made.^55
A plausible scenario may go like this. Let us start with amino acids,
which have weak catalytic activity like some other organic compounds.^56
In the prebiotic world, these activities, in concert with metal ions, could