Kinetic implications of structural modification in protein turnover

It is thought that an important function of protein turnover is to purge the cell of damaged, displaced or unwanted polypeptide molecules. A model combining kinetic equations for synthesis, degradation and alteration is employed to evaluate this proposed role for protein turnover. It is demonstrated that the degradative system need not be aimed exclusively at altered protein molecules for turnover to be capable of controlling the size both of the total population and of the altered subpopulation. These conclusions are relevant to the part played by turnover in metabolic homeostasis, adaptation and catastrophe, and for the notion of control of protein turnover through specific "tagging" of molecules destined for breakdown.