Sequential model: Difference between revisions

Revision as of 23:03, 4 March 2017

Revision as of 23:04, 4 March 2017

Line 25:

== Comparison to the MWC Model ==

The primary differentiating feature between the MWC model and KNF model lies in the scale of conformational changes.<ref name=":2" /> While both suggest that a protein's affinity for a given ligand changes upon binding of the ligand, the MWC model suggests that this occurs by a quaternary conformational change that involves the entire protein, i.e. moving from T state to R state. On the other hand, the KNF model suggests these conformational changes occur on the level of tertiary structure within the protein, as neighboring subunits change conformation with successive ligand binding.<ref>{{Cite journal|last=Ronda|first=Luca|last2=Bruno|first2=Stefano|last3=Bettati|first3=Stefano|date=2013-09-01|title=Tertiary and quaternary effects in the allosteric regulation of animal hemoglobins|url=http://www.sciencedirect.com/science/article/pii/S157096391300126X|journal=Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics|series=Oxygen Binding and Sensing Proteins|volume=1834|issue=9|pages=1860–1872|doi=10.1016/j.bbapap.2013.03.013}}</ref>

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.