Role for the leucine-responsive regulatory protein (Lrp) as a structural protein in regulating the Escherichia coli gcvTHP operon

• Published in: Microbiology (Society for General Microbiology) Vol. 145; no. 3; pp. 569 - 576
• Main Authors: Stauffer, Lorraine T, Stauffer, George V
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.03.1999; Society for General Microbiology
• Subjects: Amino Acid Oxidoreductases - biosynthesis; Amino Acid Oxidoreductases - genetics; Aminomethyltransferase; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Bacteriophage lambda - genetics; Biological and medical sciences; Carrier Proteins - biosynthesis; Carrier Proteins - genetics; DNA, Bacterial - chemistry; DNA-Binding Proteins - metabolism; Enzyme Activation; Enzyme Repression; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Genes, Reporter; Genetics; Glycine - metabolism; Hydroxymethyl and Formyl Transferases - biosynthesis; Hydroxymethyl and Formyl Transferases - genetics; Integration Host Factors; Low Density Lipoprotein Receptor-Related Protein-1; Microbiology; Multienzyme Complexes - biosynthesis; Multienzyme Complexes - genetics; Nucleic Acid Conformation; Operon; Protein Binding; Receptors, Immunologic - metabolism; Transcription Factors - metabolism; Transferases - biosynthesis; Transferases - genetics; Regulation(control); Operon; Escherichia coli; DNA binding protein; Bacteria; Molecular interaction; Regulatory sequence; Leucine responsive regulatory protein; Binding site; Gene expression; Enterobacteriaceae
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-145-3-569

Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA * George V. Stauffer. Tel: +1 319 335 7791. Fax: +1 319 335 9006. e-mail: george-stauffer@uiowa.edu ABSTRACT The Escherichia coli glycine-cleavage enzyme system ( gcvTHP and lpd gene products) provides C 1 units for cellular methylation reactions. Both the GcvA and leucine-responsive regulatory (lrp) proteins are required for regulation of the gcv operon. One model proposed for gcv regulation is that Lrp plays a structural role, bending the DNA to allow GcvA to function as either an activator or a repressor in response to environmental signals. This hypothesis was tested by replacing all but the upstream 22 bp of the Lrp-binding region in a gcvT::lacZ fusion with the l1A site from phage . Integration host factor (IHF) binds the l1A site and bends the DNA about 140°. Shifting the l1A site by increments of 1 base around the DNA helix resulted in IHF-dependent activation and repression of gcvT::lacZ expression that were face-of-the-helix dependent. Activation was also dependent on the GcvA protein, and repression was dependent on both the GcvA and GcvR proteins, demonstrating that the roles for these proteins were not altered. The results are consistent with Lrp playing primarily a structural role in gcv regulation, although they do not completely rule out the possibility that Lrp also interacts with another gcv -regulatory protein or with RNA polymerase. Keywords: gcv operon, GcvA, Lrp, IHF, DNA bending