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Importing Wikidata short description: "Type of model used in biochemistry" |
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Unlike the MWC model, the KNF model offers the possibility of "negative cooperativity".<ref name=":0" /><ref name=":2" /> This term describes a reduction in the affinity of the other binding sites of a protein for a ligand after the binding of one or more of the ligand to its subunits. The MWC model only allows for positive cooperativity, where a single conformational switch from the T to R states results in an increase in affinity for the ligand at unligated binding sites. Ligand binding to the T state thus cannot increase the amount of the protein in the T, or low-affinity, state.
Negative cooperativity is observed in a number of biologically significant molecules, including [[tyrosyl-tRNA synthetase]] and [[glyceraldehyde-3-phosphate dehydrogenase]].<ref name=":5" /><ref name=":2" /> In fact, in a systematic literature review performed in 2002 by Koshland and Hamadani, the same literature review that coined i<sup>3</sup> cooperativity, negatively cooperating proteins are seen to compose slightly less than 50% of scientifically studied proteins that exhibit cooperativity, while positively cooperating proteins compose the other, slightly greater than 50%.<ref name=":0" />
=== Functional differences in hemoglobin ===
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