The Role of Fatty Acid Vesicles in the Origin of Polymer Function

The three signature structures of cells are membranes, proteins, and nucleic acids. These structures differ markedly in their composition, so how did they first come together in one unit? And how were peptides and oligonucleotides with functions benefiting the unit selected from random sequences? I review evidence for the following scheme: The first membranes were composed of fatty acids that self-assembled in shallow bodies of fresh water into dynamic, metastable vesicles. The vesicles encapsulated peptides and oligonucleotides during cycles of dehydration and rehydration. Alternatively, polymer formation from membrane-associated monomers yielded peptide and oligonucleotide-containing vesicles. In either case, the polymer-bearing vesicles then became enriched for specific polymers due to the dynamic character of fatty acid membranes. Vesicles bearing peptides that increased vesicle stability and growth would have increased in frequency. Vesicles bearing oligonucleotides that increased the concentration of beneficial peptides would have been further favored. Complementary oligonucleotides could have stabilized peptides and reduced their diffusion out of the vesicles. They could also have directed <i>de novo</i>, templated peptide synthesis, which would have opened the path to the generation of novel peptides.