TAILIEUCHUNG - Báo cáo khoa học: pyr RNA binding to the Bacillus caldolyticus PyrR attenuation protein – characterization and regulation by uridine and guanosine nucleotides

The PyrR protein regulates expression of pyrimidine biosynthetic (pyr) genes in many bacteria. PyrR binds to specific sites in the 5¢ leader RNA of target operons and favors attenuation of transcription. Filter binding and gel mobility assays were used to characterize the binding of PyrR from Bacillus caldolyticusto RNA sequences (binding loops) from the three attenuation regions of theB. caldolyticus pyroperon. | ỊFEBS Journal pyr RNA binding to the Bacillus caldolyticus PyrR attenuation protein - characterization and regulation by uridine and guanosine nucleotides Casper M. J0rgensen1 Christopher J. Fields1 Preethi Chander2 Desmond Watt1 John W. Burgner II2 3 Janet L. Smith2 4 and Robert L. Switzer1 1 Department of Biochemistry University of Illinois Urbana USA 2 Department of BiologicalSciences Purdue University Lafayette IN USA 3 Bindley Bioscience Center Purdue University West Lafayette IN USA 4 Life Sciences Institute and Department of BiologicalChemistry University of Michigan Ann Arbor USA Keywords pyrimidine nucleotides PyrR regulation of attenuation RNA binding to proteins ultracentrifugation Correspondence R. L. Switzer Department of Biochemistry University of Illinois 600 South Mathews Urbana IL 61801 USA Fax 1 217 244 5858 Tel 1 217 333 3940 E-mail rswitzer@ Present address Bioneer A S Horsholm Denmark Received 1 November 2007 revised 30 November 2007 accepted 10 December 2007 doi The PyrR protein regulates expression of pyrimidine biosynthetic pyr genes in many bacteria. PyrR binds to specific sites in the 5 leader RNA of target operons and favors attenuation of transcription. Filter binding and gel mobility assays were used to characterize the binding of PyrR from Bacillus caldolyticus to RNA sequences binding loops from the three attenuation regions of the B. caldolyticus pyr operon. Binding of PyrR to the three binding loops and modulation of RNA binding by nucleotides was similar for all three RNAs. The apparent dissociation constants at 0 C were in the range nM in the absence of effectors dissociation constants were decreased by three- to 12-fold by uridine nucleotides and increased by 40- to 200-fold by guanosine nucleotides. The binding data suggest that pyr operon expression is regulated by the ratio of intracellular uridine nucleotides to guanosine nucleotides the effects of nucleoside addition to the

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