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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Youn, H.
Right arrow Articles by Roberts, G. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Youn, H.
Right arrow Articles by Roberts, G. P.

 Previous Article  |  Next Article 

Journal of Bacteriology, July 2008, p. 4532-4540, Vol. 190, No. 13
0021-9193/08/$08.00+0     doi:10.1128/JB.00074-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Two-State Allosteric Modeling Suggests Protein Equilibrium as an Integral Component for Cyclic AMP (cAMP) Specificity in the cAMP Receptor Protein of Escherichia coli{triangledown}

Hwan Youn,1 Junseock Koh,2 and Gary P. Roberts1*

Departments of Bacteriology,1 Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 537062

Received 15 January 2008/ Accepted 21 April 2008

Activation of the cAMP receptor protein (CRP) from Escherichia coli is highly specific to its allosteric ligand, cAMP. Ligands such as adenosine and cGMP, which are structurally similar to cAMP, fail to activate wild-type CRP. However, several cAMP-independent CRP variants (termed CRP*) exist that can be further activated by both adenosine and cGMP, as well as by cAMP. This has remained a puzzle because the substitutions in many of these CRP* variants lie far from the cAMP-binding pocket (>10 Å) and therefore should not directly affect that pocket. Here we show a surprising similarity in the altered ligand specificity of four CRP* variants with a single substitution in D53S, G141K, A144T, or L148K, and we propose a common basis for this phenomenon. The increased active protein population caused by an equilibrium shift in these variants is hypothesized to preferentially stabilize ligand binding. This explanation is completely consistent with the cAMP specificity in the activation of wild-type CRP. The model also predicts that wild-type CRP should be activated even by the lower-affinity ligand, adenosine, which we experimentally confirmed. The study demonstrates that protein equilibrium is an integral factor for ligand specificity in an allosteric protein, in addition to the direct effects of ligand pocket residues.

* Corresponding author. Mailing address: Department of Bacteriology, 1550 Linden Drive, University of Wisconsin-Madison, Madison, WI 53706. Phone: (608) 262-3567. Fax: (608) 262-9865. E-mail: groberts{at}bact.wisc.edu

{triangledown} Published ahead of print on 2 May 2008.

Journal of Bacteriology, July 2008, p. 4532-4540, Vol. 190, No. 13
0021-9193/08/$08.00+0     doi:10.1128/JB.00074-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Popovych, N., Tzeng, S.-R., Tonelli, M., Ebright, R. H., Kalodimos, C. G. (2009). Structural basis for cAMP-mediated allosteric control of the catabolite activator protein. Proc. Natl. Acad. Sci. USA 106: 6927-6932 [Abstract] [Full Text]  


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