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Journal of Bacteriology, April 2001, p. 2204-2211, Vol. 183, No. 7
Microbiology Department, Brigham Young
University, Provo, Utah 84602-5253
Received 8 November 2000/Accepted 12 January 2001
Two-component signaling proteins are involved in transducing
environmental stimuli into intracellular signals. Information is
transmitted through a phosphorylation cascade that consists of a
histidine protein kinase and a response regulator protein. Generally,
response regulators are made up of a receiver domain and an output
domain. Phosphorylation of the receiver domain modulates the activity
of the output domain. The mechanisms by which receiver domains control
the activities of their respective output domains are unknown. To
address this question for the PhoB protein from Escherichia
coli, we have employed two separate genetic approaches, deletion
analysis and domain swapping. In-frame deletions were generated within
the phoB gene, and the phenotypes of the mutants were
analyzed. The output domain, by itself, retained significant ability to
activate transcription of the phoA gene. However, another deletion mutant that contained the C-terminal
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.7.2204-2211.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Genetic Evidence that the
5 Helix of the
Receiver Domain of PhoB Is Involved in Interdomain
Interactions
and
-helix of the receiver domain (
5) in addition to the entire output domain was unable to
activate transcription of phoA. This result suggests that
the
5 helix of the receiver domain interacts with and inhibits the output domain. We also constructed two chimeric proteins that join
various parts of the chemotaxis response regulator, CheY, to PhoB.
A chimera that joins the N-terminal ~85% of CheY's receiver domain
to the
5-
5 loop of PhoB's receiver domain displayed
phosphorylation-dependent activity. The results from both sets of
experiments suggest that the regulation of PhoB involves the
phosphorylation-mediated modulation of inhibitory contacts between the
5 helix of its unphosphorylated receiver domain and its output domain.
*
Corresponding author. Mailing address: Microbiology
Department, Brigham Young University, 775 WIDB, Provo, UT 84602-5253. Phone: (801) 378-8793. Fax: (801) 378-9197. E-mail:
bill_mccleary{at}byu.edu.
Present address: University of Utah, Huntsman Cancer Institute,
Salt Lake City, UT 84101.
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