Fold Properly: Do Not Bend or Mutilate
The properties of all organisms depend on the proteins they contain. These include the structural proteins as well as enzymes. Even though a cell may be able to synthesize a protein, unless that protein is folded correctly and achieves its correct shape, it will not function properly. A major challenge associated with the molecules of life is to understand how proteins fold correctly. This is the protein folding problem. Not only is this an important problem from a purely scientific point of view, but a number of serious neurodegenerative diseases appear to be a result of protein misfolding. These include Alzheimer disease and the neurode-generative diseases caused by prions. If we could understand how proteins fold correctly, we might be able to prevent such diseases.
The information that determines how a protein folds into its three-dimensional configuration is contained in the sequence of its amino acids. It is not yet possible, however, to predict accurately how a protein will fold from its amino acid sequence. The folding occurs in a matter of seconds after the protein is synthesized. The protein folds rapidly into its secondary structure and then more slowly into its tertiary structure. In these slower reactions, many different adjustments of the amino acid side chains are tried out before the protein assumes the correct tertiary structure. The proteins that help other proteins fold correctly, the chaperones, play their role in the slow stage. The cell discards improperly folded proteins. Enzymes, called proteases, recognize improperly folded proteins and degrade them. The protein-folding problem has such important implications for medicine and is so challenging a scientific question, that a super-computer is being built to help solve the problem of predicting the three-dimensional structure of a protein from its amino acid sequence. ■ prions, p. 365
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