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Journal of Bacteriology, September 1998, p. 4865-4871, Vol. 180, No. 18
Department of Microbiology, The University of
Iowa, Iowa City, Iowa 52242
Received 6 April 1998/Accepted 22 July 1998
The GcvA protein is required for both glycine-mediated activation
and purine-mediated repression of the gcvTHP operon. Random and site-directed PCR mutagenesis was used to create nucleotide changes
in gcvA to identify residues of the protein involved in activation, repression, and DNA binding. Single amino acid
substitutions at L30 and F31 cause a defect in activation of a
gcvT-lacZ fusion but have no effect on repression or DNA
binding. Single amino acid substitutions at V32 and S38 cause the loss
of binding of GcvA to DNA. A deletion of the carboxy-terminal 14 amino
acids of GcvA results in the loss of purine-mediated repression and, consequently, a constitutive activation of a gcvT-lacZ
fusion. The results of this study partially define regions of GcvA
involved in activation, repression, and DNA binding and demonstrate
that these functions of GcvA are genetically separable.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutational Analysis of the Transcriptional Regulator GcvA:
Amino Acids Important for Activation, Repression, and DNA
Binding
*
Corresponding author. Mailing address: Department of
Microbiology, The University of Iowa, Iowa City, IA 52242. Phone: (319) 335-7791. Fax: (319) 335-9006. E-mail:
george-stauffer{at}uiowa.edu.
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