Intrinsic physical instability of the proteins with short half-time: possible role in aging and in carcinogenesis

Different proteins have vastly different lifetime in cells, some survive as long as or even longer than the cell does, whereas others survive for just minutes. Proteins showing short half-times play an extremely important role as cellular regulators, in particular in controlling cell mitosis and in carcinogenesis. These proteins probably possess an intrinsic physical instability, i.e. they are biologically active only while being in a meta-stable non-equilibrium state resulting from the very mechanisms of protein biosynthesis on ribosomes. Aging of these proteins consists of internal equilibration through protein chain folding rather than in accumulation of errors due to intermolecular interactions. We want to attract more attention to such fast (short-lived) proteins. The question of what determines these protein lifetimes is of practical as well as theoretical interest.