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Cooperativity is a phenomenon displayed by systems involving identical or near-identical elements, which act dependently of each other, ... In systems biology, ...
The first description of cooperative binding to a multi-site protein was developed by A.V. Hill. [4] Drawing on observations of oxygen binding to hemoglobin and the idea that cooperativity arose from the aggregation of hemoglobin molecules, each one binding one oxygen molecule, Hill suggested a phenomenological equation that has since been named after him:
The Hill coefficient, or , may describe cooperativity (or possibly other biochemical properties, depending on the context in which the Hill equation is being used). When appropriate, [clarification needed] the value of the Hill coefficient describes the cooperativity of ligand binding in the following way:
In evolution, cooperation is the process where groups of organisms work or act together for common or mutual benefits. It is commonly defined as any adaptation that has evolved, at least in part, to increase the reproductive success of the actor's social partners. [1]
The sequential model (also known as the KNF model) is a theory that describes cooperativity of protein subunits. [1] It postulates that a protein's conformation changes with each binding of a ligand, thus sequentially changing its affinity for the ligand at neighboring binding sites.
This model explains sigmoidal binding properties (i.e. positive cooperativity) as change in concentration of ligand over a small range will lead to a large increase in the proportion of molecules in the R state, and thus will lead to a high association of the ligand to the protein. It cannot explain negative cooperativity.
Many animal species cooperate with each other in mutual symbiosis.One example is the ocellaris clownfish, which dwells among the tentacles of Ritteri sea anemones.The anemones provide the clownfish with protection from their predators (which cannot tolerate the stings of the sea anemone's tentacles), while the fish defend the anemones against butterflyfish (which eat anemones)
This model is supported by positive cooperativity where binding of one ligand increases the ability of the enzyme to bind to more ligands. The model is not supported by negative cooperativity where losing one ligand makes it easier for the enzyme to lose more. In the sequential model there are many different global conformational/energy states ...