Anfinsen's dogma
Anfinsen's dogma (also known as the thermodynamic hypothesis) is a postulate in molecular biology that, at least for small globular proteins, the native structure is determined only by the protein's amino acid sequence. The dogma was championed by the Nobel Prize LaureateChristian B. Anfinsen from his research on the folding of ribonuclease A. The postulate amounts to saying that, at the environmental conditions (temperature, solvent concentration and composition, etc.) at which folding occurs, the native structure is a unique, stable and kinetically accessible minimum of the free energy. The three conditions:
How the protein reaches this structure is the subject of the field of protein folding, which has a related concept called Levinthal's paradox. The Levinthal paradox states that the number of possible conformations available to a given protein is astronomically large, such that even a small protein of 100 residues would require more time than the universe has existed (1016 seconds) to explore all possible conformations and choose the appropriate one, it would also arguably make computational prediction of protein structures under the same basis unfeasible if not impossible.
Also, some proteins need the assistance of another protein called a chaperone protein to fold properly. It has been suggested that this disproves Anfinsen's dogma. However, the chaperones do not appear to affect the final state of the protein; they seem to work primarily by preventing aggregation of several protein molecules before the protein is folded.
Prions are an exception to Anfinsen's dogma. Prions are stable conformations of proteins which differ from the native folding state. In Bovine spongiform encephalopathy (Mad Cow Disease), native proteins re-fold into a different stable conformation, which causes fatal amyloid buildup. Other amyloid diseases, including Alzheimer's disease and Parkinson's disease, are also exceptions to Anfinsen's dogma.
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