Kinetic Devices in Protein Synthesis, DNA Replication, and Mismatch Repair

Enzymes are reputed to accomplish ighly special-ized tasks, thanks to an active site whose shape matches closely that of the substrate. The cell also needs general practitioner enzymes, just so for the tasks requiring the highest accuracy. Thus, a single macromolecular s-sembly, the ribosome, must select a correct tRNA in response to 61 different codons. A polymerase must insert the correct nucleotide in response to each of the four nucleotides of the template. For such situations, designing a clever binding site is not enough. The great-est attention must be paid to the "wiring diagram " of the reaction mechanism and to the time window allo-cated to each step. The following intuitive example illustrates the importance of appropriate timing. After a DNA replication error is made, mismatch binding