Chemical Steps in the Selective Inactivation and Degradation of Glutamine Phosphoribosylpyrophosphate Amidotransferase in Bacillus subtilis

Abstract

The mechanism and regulation of selective intracellular proteolysis present major unsolved problems to the field of biochemical regulation of enzyme activity. A number of useful experimental approaches may be taken toward solving these problems. One such approach is to characterize the proteolytic apparatus of the cell by isolation and biochemical characterization of individual proteolytic enzymes and their inhibitors. This approach is strengthened in studies with microorganisms by use of genetic and physiological analysis of protease-deficient mutants. A second means of studying proteolysis consists in labeling the proteins of the cell with a radioactive amino acid and determining the physiological variables that influence the release of the amino acid from proteins during their degradation in the presence of a large excess of the nonradioactive amino acid. A third approach, which we have chosen, is to focus on specific substrates of selective proteolytic events and to attempt to dissect the inactivation and degradation of a given protein into discrete biochemical steps. Ultimately, the objective is to reconstruct the degradation process from purified components in a manner that faithfully reproduces its regulation and physiological requirements.