Published online by Cambridge University Press: 15 February 2011
Complex organized systems evolved from the prebiotic soup approximately three billion years ago, relying on simple molecules which spontaneously and synergistically combine to accomplish certain tasks. As life evolved, the sophistication of these interactions also increased. Organisms evolved by linking the needed functional groups together in proteins to improve the efficiency of the process, and now rely almost exclusively on protein interactions to accomplish needed tasks. It is for this reason that considerable effort has been expended on understanding how such complexes are formed and how the individual components contribute to overall function. The code for these interactions lies buried in the amino acid sequences of the constituent proteins. Biologists are beginning to unravel the secrets of this code, and see how small changes to individual residues can affect the overall stability and function of the complex.