This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Dirla, S.
Right arrow Articles by Schleif, R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Dirla, S.
Right arrow Articles by Schleif, R.

 Previous Article  |  Next Article 

Journal of Bacteriology, April 2009, p. 2668-2674, Vol. 191, No. 8
0021-9193/09/$08.00+0     doi:10.1128/JB.01529-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Constitutive Mutations in the Escherichia coli AraC Protein {triangledown}

Stephanie Dirla, John Yeh-Heng Chien, and Robert Schleif*

Biology Department, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218

Received 29 October 2008/ Accepted 31 January 2009

The Escherichia coli AraC protein represses and induces the araBAD operon in response to the absence or presence of L-arabinose. Constitutive mutations in the AraC gene no longer require the presence of L-arabinose to convert AraC from its repressing to its inducing state. Such mutations were isolated directly by virtue of their constitutivity or by their resistance to the nonmetabolizable arabinose analog, D-fucose. The majority of the constitutive mutations lie within the same residues of the N-terminal regulatory arm of AraC. Two, however, were found in the core of the dimerization domain. As predicted by the light switch mechanism of AraC, constitutive mutations increase the susceptibility of the N-terminal arms to digestion by trypsin or chymotrypsin, suggesting that these mutations weaken or disrupt the arm structure required for repression by AraC. Fluorescence, circular dichroism, and cysteine reactivity measurements show that the constitutive mutations in the core of the dimerization domain lead to a weakening of the support for the arms and reduce the stability of the minus-arabinose arm structure. These mutations also weaken the interaction between the two-helix bundle and the β-barrel subdomains of the dimerization domain and reduce the structural stability of the β-barrels.

* Corresponding author. Mailing address: Biology Department, Johns Hopkins University, 3400 North Charles St., Baltimore, MD 21218. Phone: (410) 516-5206. Fax: (410) 516-5213. E-mail: schleif{at}jhu.edu

{triangledown} Published ahead of print on 13 February 2009.

Journal of Bacteriology, April 2009, p. 2668-2674, Vol. 191, No. 8
0021-9193/09/$08.00+0     doi:10.1128/JB.01529-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»