Function and Environmental Regulation ofkpsF, the First Gene of the Region One Operon of Escherichia Coli K1
Cieslewicz, Michael John
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https://hdl.handle.net/2142/87641
Description
Title
Function and Environmental Regulation ofkpsF, the First Gene of the Region One Operon of Escherichia Coli K1
Author(s)
Cieslewicz, Michael John
Issue Date
1997
Doctoral Committee Chair(s)
Vimr, Eric R.
Department of Study
Veterinary Pathobiology
Discipline
Veterinary Pathobiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
Temperature is the only environmental stimulus currently known to affect K1 capsule expression. Capsule is maximally expressed at body temperature (37$\sp\circ$C or 98.6$\sp\circ$F), but is turned off at temperatures commonly encountered in the external environment, below about 26$\sp\circ$C. Expression of the first gene of the region 1 operon, kpsF, is controlled by thermal regulation of a $\sigma7$0-type promoter. Thus, thermoregulation of the region 1 operon appears to involve a new mechanism controlling the in vivo expression of an important virulence factor. A promoterless non-polar kanamycin cassette inserted into kpsF has no detectable phenotype when mutant cells were cross-streaked against the K1 capsule specific bacteriophage, K1F. However, more sensitive assays for the capsule exhibited an intermediate capsule phenotype, including reduced plaque size and decreased surface expression of polysialic acid. These results indicate that KpsF is not obligatory for capsule synthesis or transport, although KpsF may be necessary for normal transport and assembly of a wild type capsule. A potential nucleotide binding site and helix-turn-helix motif predicted from the kpsF sequence are primary structural features of KpsF that are consistent with its hypothesized regulatory function. Two other KpsF homologs, GutQ and Orf328, have been identified in Escherichia coli, while additional homologs have been found in other genera suggesting that KpsF is a member of a new family of regulatory proteins that may be of general importance in diverse host-microbe interactions.
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