THE FIRST LIVING SYSTEMS - A BIOENERGETIC PERSPECTIVE

Authors
Citation
Dw. Deamer, THE FIRST LIVING SYSTEMS - A BIOENERGETIC PERSPECTIVE, Microbiology and molecular biology reviews, 61(2), 1997, pp. 239
Citations number
168
Categorie Soggetti
Microbiology
Volume
61
Issue
2
Year of publication
1997
Database
ISI
SICI code
Abstract
The first systems of molecules having the properties of the living sta te presumably self-assembled from a mixture of organic compounds avail able on the prebiotic Earth. To carry out the polymer synthesis charac teristic of all forms of life, such systems would require one or more sources of energy to activate monomers to be incorporated into polymer s. Possible sources of energy for this process include heat, light ene rgy, chemical energy, and ionic potentials across membranes These ener gy sources are explored here, with a particular focus on mechanisms by which self-assembled molecular aggregates could capture the energy an d use it to form chemical bonds in polymers. Based on available eviden ce, a reasonable conjecture is that membranous vesicles were present o n the prebiotic Earth and that systems of replicating and catalytic ma cromolecules could become encapsulated in the vesicles. In the laborat ory, this can be modeled by encapsulated polymerases prepared as lipos omes. By an appropriate choice of lipids, the permeability proper-ties of the liposomes can be adjusted so that ionic substrates permeate at a sufficient rate to provide a source of monomers for the enzymes, wi th the result that nucleic acids accumulate in the vesicles. Despite t his progress, there is still no clear mechanism by which the free ener gy of light ion gradients, or redox potential can be coupled to polyme r bond formation in a protocellular structure.