Autogenous regulation of gene expression.

A new term, autogenous regulation, is used to describe a phenomenon that is not a new discovery but rather is newly appreciated as a mechanism common to a number of systems in both prokaryotic and eukaryotic organisms. In this mechanism the product of a structural gene regulates expression of the operon in which that structural gene resides. In many (perhaps all) cases, the regulatory gene product has several functions, since it may act not only as a regulatory protein but also as an enzyme, structural protein, or antibody, for example. In a few cases, this protein is the multimeric allosteric enzyme that catalyzes the first step of a metabolic pathway, gearing together the two most important mechanisms for controlling the biosynthesis of metabolites in bacterial cells-feedback inhibition and repression. Autogenous regulation may provide a mechanism for amplification of gene expression (84); for severe and prolonged inactivation of gene expression (85); for buffering the response of structural genes to changes in the environment (45, 52); and for maintaining a constant intracellular concentration of a protein, independent of cell size or growth rate (86). Thus, autogenous regulation provides the cell with means for accomplishing a number of different regulatory tasks, each suited to better satisfying the needs of the organism for its survival.