This week on Journal Club session Reinoud Maex will talk about a paper "Packaging Life: The Origin of Ion-Selective Channels".
Most articles dealing with early life focus on its chemical basis and the evolution of proteins, RNA, DNA, and other metabolic products. This essay, however, is concerned primarily with the energy required to produce and maintain the essential life chemicals, and the necessity to confine them in a cell where they can function cooperatively. It seems likely that life evolved in proximity to the undersea vents discovered by the submersible craft Alvin of the Woods Hole Oceanographic Institute (Woods Hole, MA). Bacteria were probably the original life form, growing in mats near the vents. Some advantages of the vents as starting points for life are:
- Plentiful water and essential ions. We are ~60% salt water.
2. Plenty of chemical elements, many out of equilibrium and ready to combine. From one point of view, chemistry is simply the search of electrons, e.g., the two around a hydrogen molecule, for vacancies as close as possible to a nucleus with many protons, e.g., oxygen, or less avid electron gatherers, e.g., nitrogen, carbon, sulfur, or phosphorus. Eighteen of the 20 AAs contain only hydrogen, carbon, nitrogen, and oxygen; and the remaining two require sulfur in addition. DNA and RNA require, in addition, phosphorus. In short, it is not necessary to dip far into the periodic table to make most of the life chemicals.
3. Energy can be derived from combining chemicals issuing from the vent, as in a fuel cell, which derives energy by passing electrons from hydrogen to oxygen.
4. The water near a vent is warm, speeding experiments in the evolution of life chemicals.
Given these essentials, it is easy to imagine that life developed over a period of time, say a billion years. J. D. Sutherland, who first succeeded in synthesizing RNA, was quoted as saying: ‘‘My assumption is that we are here on this planet as a fundamental consequence of organic chemistry.So it must be chemistry that wants to work’’ (1). This essay starts at the point where early chemistry has done its work. It deals with the packaging of the life chemicals, the problems that arise from packaging, and energy production.
- Clay M. Armstrong "Packaging life: the origin of ion-selective channels.", 2015, Biophys. J. 109, 173-177.