How Genes Work to Regulate Cell Activity

Protein structure determinations perfectly complement genomic information. The proteins revealed in these structures are marvelous molecular machines. Each consists of a chain of amino acids (or several chains) whose sequence is encoded in the genome. Once constructed, that chain folds into a specific three-dimensional structure to form a molecular motor, a sturdy filament, a chemical factory or any of thousands of molecule-sized gizmos. In the past few decades, structural biologists have determined the structures of thousands of proteins, revealing the details of their function at the atomic level. Two types of information--genomic sequences and protein structures--have become abundant and have transformed the study of molecular biology Genome sequences contain instructions for building molecules, cells and, ultimately, entire organisms. The genome is the blueprint for all of the proteins of an organism--this is essential information because proteins control nearly all of the processes of living cells. (p.34)

Protein may have large-scale effects on the cell's overall function. In order to avoid volume alterations, all cells have adapted mechanisms to equalize the osmotic activity between their internal and external environments. For many years, scientists believed these mechanisms relied mainly on the influx and outflow of small, charged inorganic particles, primarily the ions of sodium, potassium, hydrogen and chloride. Organic molecules that traverse membranes during the course of normal cellular function can also be cosmetically active and so affect cell volume. In part, this new understanding comes from a re-examination of the osmotic pressures exerted by the normal substrates and by-products of everyday metabolism. (p.38) For example, amino acids, the components of proteins, are transported across cell membranes and can therefore affect the dynamics of cell-volume regulation. The incorporation of amino acids into proteins or the breakdown of proteins into their constituent amino acids can have profound - and opposite - effects on cell volume.

1. Alberts, B., D. Bray, J. Lewis, M. Raff, K. Roberts and J. D. Watson.. Molecular Biology of the Cell (third edition). (New York: Garland Publishing, 1994). ...

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