Section 23.4.6.4. Summary

The few examples illustrated above provide diverse views of the ways in which Nature can use water molecules as integral parts of macromolecular interactions. Water molecules can be involved in specificity and recognition, in thermodynamics of binding and affinity, in the cooperative behaviour of allosteric proteins, and in catalysis. Not only do the specific examples illustrate general roles possible for water molecules in the context of a given type of macromolecule, such as proteins or nucleic acids, but they are often representative of any macromolecular system. For example, the role of water in recognition and specificity illustrated above for protein–DNA interactions has also been observed in the L-arabinose-binding protein interaction with specific sugar molecules (Quiocho et al., 1989). Clearly, water molecules are involved so intimately, and in so many different ways, with the formation of molecular complexes that it is not possible to understand the formation process and the function of the complex without taking into account the role of this universal solvent.