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Research Paper |
Department of Microbiology, The University of Iowa, Iowa City, IA 52242, USA1
Author for correspondence: George V. Stauffer. Tel: +1 319 335 7791. Fax: +1 319 335 9006. e-mail: george-stauffer{at}uiowa.edu
The Escherichia coli gcvTHP operon is under control of the LysR-type transcriptional regulator GcvA. GcvA activates the operon in the presence of glycine and represses the operon in its absence. Repression by GcvA is dependent on a second regulatory protein, GcvR. Generally, LysR-type transcriptional regulators bind to specific small co-effector molecules which results in either their altered affinity for specific binding sites on the DNA or altered ability to bend the DNA, resulting in either activation or repression of their respective operons. This study shows that glycine, the co-activator for the gcv operon, does not alter either GcvAs ability to bind DNA nor its ability to bend DNA. Rather, glycine binds to GcvR, disrupting a GcvA/GcvR interaction required for repression and allowing GcvA activation of the gcvTHP operon. Amino acid changes in GcvR that reduce glycine binding result in a loss of glycine-mediated activation in vivo.
Keywords: gcvTHP, GcvA, GcvR, glycine, repression
Abbreviations: AP, ampicillin; C1, one-carbon; co-ppt, co-precipitation; gcv, gcvTHP operon; GCV, glycine cleavage; GMS, gel mobility shift; LTTR, LysR-type transcriptional regulator; RNAP, RNA polymerase; TPEG, phenylethyl-ß-D-thiogalactoside
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