Fundamental Aspects of T7 RNA Polymerase Structure and Mechanism

The enzymes that synthesize the nucleic acids — the polymerases — execute a reaction of fascinating complexity. Early work on these enzymes was carried out by biochemists who approached them from a classical, enzymological perspective and emphasized physical purity and quantitative assays (Korberg 1989). However, because of their roles in gene replication and expression, these enzymes also attracted the interest of molecular biologists who emphasized an approach that, while perhaps less quantitative, led more readily to qualitative answers for questions of broad significance. This was necessary, for an insistence on physical purity of all reaction components or rigorous formulation of kinetic mechanisms would have made it very difficult to make rapid progress in the study of these large and fragile macromolecules and the complex reactions they carry out. While necessary and productive, these more qualitative studies necessarily left our understanding of some aspects of polymerase mechanism rather sketchy.