Maintaining life and health by natural selection of protein molecules

A concept for a life and health-preserving principle is presented, with reference to evolutionary, medical, and biochemical observations. Life comprises two basic phenomena: it unfolds over longer periods at the population level, and is sustained for the duration of individual life spans. The evolution of life within populations by means of natural selection of individuals is central to Darwin's theory of evolution. An important component of maintaining individual life is proposed here to be the natural selection of molecular components-the proteins, a process of preferred removal of denatured and old, synonymous with the selection of younger, functional molecules. The proteins of the cell are committed to fulfilling all the tasks programmed by the genome while continuously maintaining all appropriate cellular functions, including protecting the DNA. Physiological and environmental influences accelerate the breakdown of aged protein molecules, driving this renewal process so that the cell can maintain its protein stock at high-performance levels. The principle of selection makes the incredible dynamics of continual protein turnover, and hence not only the preservation of life, but the maintenance of health in individual beings, comprehensible. Arguments are presented to counter the hypothesis that protein breakdown is a stochastic, random process governed by first-order kinetics.