39  Production of proteins

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It is not sufficient that all proteins produced in a living cell are folded correctly and addressed correctly. It is also necessary to produce the correct quantity of each protein. If it were not possible for a cell to stop production of a certain protein at the correct time, this would have an effect similar to slowly burning down the whole house instead of simply adding some wood to the fire in the fireplace. The mechanism that stops and starts production of proteins must be correctly functional in each cell from the very beginning.

It cannot be taken for granted that the production of each individual protein is started and stopped at the correct time (1). Life begins when the cell contains the correct quantity of each protein, when all proteins are correctly folded and integrated at the correct location.

However, as life begins, the proteins also begin to wear out. It is then necessary for the cell to be capable of replacing the worn-out proteins with newly-produced proteins. This mechanism must also be present and fully functioning from the very beginning.

DNA regulation sequence and regulator proteins:
The most important feature for starting and stopping protein production consists of the regulation sequences on the DNA. These sections of the DNA have the function of telling the cells when to start and stop producing the various proteins. However, the DNA itself cannot start or stop protein production. This requires cooperation with special regulator proteins that are folded in such a manner that they precisely match a special section of the DNA (2).

The DNA regulation sequence and the regulating proteins require one another mutually. Both must be perfectly coordinated to correctly start and stop production of the associated proteins.  Actually, they form a switch, an irreducible complex system that is essential for life.

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(1) S. Aldridge, The Thread of Life. The story of genes and genetic engineering, Cambridge University Press, Cambridge, UK, 1996, pages 47–53.
(2) B. Alberts, D. Bray und A. Johnson et al., Essential Cell Biology. An Introduction to the Molecular Biology of the Cell, Garland Publishing Inc., New York (USA), 1998, pages 259–262.

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