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Comparison of the mechanism of transmembrane signaling in bacterial chemoreceptors and sensor kinases

Membrane-bound receptors transmit information from the cell exterior to the cell interior.
Bacterial receptors capable of transmitting this information include sensor kinases, which
control gene expression via response regulators, and methyl-accepting chemotaxis proteins
(MCPs), which control rotation of the flagellar motor. These receptors, which have a
similar general architecture and function, are predicted to share similar mechanisms of
transmembrane signaling. The majority of such work has been conducted on MCPs. Our
goal is to extend this work to the closely related sensor kinases by creating functional
hybrid transducers. I show that a chimeric protein (Nart) that joins the periplasmic, ligandbinding
domain of the sensor kinase NarX (nitrate/nitrite sensor) to the cytoplasmic
signaling domain of the chemoreceptor Tar is capable of modulating flagellar rotation in
response to both nitrate and nitrite. Consistent with the properties of NarX, our Nart elicits
a stronger response to nitrate than to nitrite. Introduction of mutations into a highly
conserved periplasmic region affects Nart signaling in a fashion that is consistent with the
effects seen in NarX. I also present the first example of a substitution in a presumed
ligand-binding domain that confers a reverse-signal phenotype for both nitrate and nitrite in Nart. These results support the hypothesis that the key aspects of transmembrane
signaling are closely similar in homodimeric bacterial chemoreceptors and sensor kinases.
Date30 October 2006
CreatorsWard, Scott Michael
ContributorsManson, Michael D.
PublisherTexas A&M University
Source SetsTexas A and M University
Detected LanguageEnglish
TypeBook, Thesis, Electronic Dissertation, text
Format3015829 bytes, electronic, application/pdf, born digital

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