ABSTRACT
As we have seen in Chapter 2, a multidomain structure has a powerful evolutionary advantage: it allows proteins to acquire new functions, and it gives proteins suitable concave binding sites for binding ligands or allosteric effectors. The same is almost equally true of oligomeric proteins, to which we now turn. Most proteins are in fact oligomers: there must therefore be a powerful advantage to being oligomeric. As we shall see, there are actually several quite different advantages, of which the two main are that it allows proteins to be allosteric (Section 3.2) and that it allows proteins to bind cooperatively (Section 3.3). It is also presumably the case that constraints within a symmetric homo-oligomeric interaction make it simple for a homo-oligomeric interaction to evolve [2]: that is, oligomers can evolve rapidly and easily (Figure 3.1). Evolution never ignores something that can provide a quick gain with little effort!
