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Concept
Allosteric regulation
Résumé
In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site.
The site to which the effector binds is termed the allosteric site or regulatory site. Allosteric sites allow effectors to bind to the protein, often resulting in a conformational change and/or a change in protein dynamics. Effectors that enhance the protein's activity are referred to as allosteric activators, whereas those that decrease the protein's activity are called allosteric inhibitors.
Allosteric regulations are a natural example of control loops, such as feedback from downstream products or feedforward from upstream substrates. Long-range allostery is especially important in cell signaling. Allosteric regulation is also particularly important in the cell's ability to adjust enzyme activity.
The term allostery comes from the Ancient Greek allos (), "other", and stereos (), "solid (object)". This is in reference to the fact that the regulatory site of an allosteric protein is physically distinct from its active site.
Many allosteric effects can be explained by the concerted MWC model put forth by Monod, Wyman, and Changeux, or by the sequential model (also known as the KNF model) described by Koshland, Nemethy, and Filmer. Both postulate that protein subunits exist in one of two conformations, tensed (T) or relaxed (R), and that relaxed subunits bind substrate more readily than those in the tense state. The two models differ most in their assumptions about subunit interaction and the preexistence of both states. For proteins in which subunits exist in more than two conformations, the allostery landscape model described by Cuendet, Weinstein, and LeVine, can be used. Allosteric regulation may be facilitated by the evolution of large-scale, low-energy conformational changes, which enables long-range allosteric interaction between distant binding sites.
Source officielle
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