The School of Molecular and Cellular Biology at the University of Illinois at Urbana-Champaign

Our research program studies the regulation of metabolism as exemplified by the control of biosynthetic enzymes during bacterial growth and differentiation. A second research theme is the study of the active sites, mechanism of catalysis and of allosteric regulation of enzymes of nucleotide biosynthesis.

A current focal point is the regulation of transcription of the ten-cistron pyrimidine biosynthetic (pyr) operon in Bacillus subtilis, which we have shown to be governed by the protein, called PyrR, encoded by the first gene of the operon. This protein, which also catalyzes uracil phosphoribosyltransferase activity, promotes transcriptional termination at three attenuation sites in the pyr operon. PyrR acts by binding in a uridine nucleotide dependent manner to specific sites on pyr mRNA and altering its conformation, so that a transcription terminator is formed. The PyrR protein has been purified to homogeneity and its 3D structure has been determined. Our current objectives are to characterize the PyrR protein, the RNA to which it binds, and the PyrR-RNA interaction at high resolution. The regulatory activities of PyrR are being examined by physical, biochemical and genetic methods. We are examining regulation of pyr genes by PyrR in other bacteria, including clinically important pathogens.

Our laboratory also studies the regulation by transcriptional antitermination of the B. subtilis pyrG gene, which encodes CTP synthase. This gene is regulated independently of the pyr operon by a highly novel mechanism, which involves reiterative transcription or "transcriptional slippage" and no regulatory protein. We are extending our understanding of this mechanism by genetic and biochemical approaches.

Prof. Switzer no longer accepts new researchers to work in his laboratory, as it will be closed soon.