Molecular conformations

Proteins are not static 3-dimensional objects. They undergo conformational changes and those changes can be related to a change of function. Even for small conformational changes there can be a significant change in energy. The binding of one protein to another can allosterically change the latter, such that other proteins are able to bind. This allows the formation of a functional complex. The proteins that make up the complex will not be permanently bound: they come and go as necessary. The determining factor in the formation of a complex is the residence time of a protein. If protein mis-folds then the system of checks and balances known as proteostasis ensures that the protein in question is degraded. The affinity of two proteins is determined by their respective concentrations and proteins can sequester in local groups to increase their effective concentrations. This colocalization is now recognised as an important phenomenon. The functional ability of proteins can be enhanced by PTMs. These modifications of proteins form one of the pillars of epigenetics.