Allosteric regulation

The term allostery - from the Greek allos ἄλλως ( otherwise) and στερεός Stereos ( place ), meaning " the other place " - stemming from the field of biochemistry, where the protein function.

It is used differently in the literature. He is initially valid for proteins with a regulatory active molecules ( effectors ) bind elsewhere as their substrate ( enzyme ) and its central ligand (carrier or receptor ). Cases in which the binding strength of which depends on the number of previously bonded substrate or ligand molecules are also included in this.

Allosterie initially meant the change in conformation under the influence of the active site / binding site. Some authors believe that a cooperative interaction between separate subunits of a ( oligomeric ) protein is necessary for the allosteric effect in any case; then likely that in the monomeric proteins no allosteric effects. However, known changes in the spatial structure of small molecules that may have an impact on the active site and in such proteins. It has therefore become customary to subsume these phenomena under the concept of allostery. For the example of phosphofructokinase, this means that each polypeptide chain is seen here as a fusion of two subunits (C and R). Each of these subunits binds ATP, C, in his capacity as a substrate (coenzyme ) and R in his capacity as an allosteric inhibitor.

Prototype of an allosteric hemoglobin protein, wherein the bond strength of the oxygen (O2) by a number of effectors, and especially depends on how many of the four O2 binding sites are already occupied. At higher Sauerstoff-konzentrationen/-beladungen is the transition from a low - affinity "T- state" (T for tense, Eng. = Taut, tense ) in the high-affinity "R- state" (R for relaxed, Eng. = relaxed ) was recorded. The fact that subsequent O2 molecules are becoming more closely linked, also called positive cooperativity. The Hill coefficient is a measure of the cooperativity.