Affiliation:
1. Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
2. Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
Abstract
ABSTRACT
The
Yersinia enterocolitica
Ysa type III secretion system (T3SS) is associated with intracellular survival, and, like other characterized T3SSs, it is tightly controlled. Expression of the
ysa
genes is only detected following growth at low temperatures (26°C) and in high concentrations of sodium chloride (290 mM) in the medium. The YsrSTR phosphorelay (PR) system is required for
ysa
expression and likely responds to NaCl. During our investigations into the Ysr PR system, we discovered that genes YE3578 and YE3579 are remarkably similar to
ysrR
and
ysrS
, respectively, and are probably a consequence of a gene duplication event. The amino acid differences between YE3578 and
ysrR
are primarily clustered into two short regions. The differences between YE3579 and
ysrS
are nearly all located in the periplasmic sensing domain; the cytoplasmic domains are 98% identical. We investigated whether these paralogs were capable of activating
ysa
gene expression. We found that the sensor paralog, named DygS, is capable of compensating for loss of
ysrS
, but the response regulator paralog, DygR, cannot complement a
ysrR
gene deletion. In addition, YsrR, but not DygR, interacts with the histidine phosphorelay protein YsrT. Thus, DygS likely activates
ysa
gene expression in response to a signal other than NaCl and provides an example of a phosphorelay system in which two sensor kinases feed into the same regulatory pathway.
IMPORTANCE
All organisms need mechanisms to promote survival in changing environments. Prokaryotic phosphorelay systems are minimally comprised of a histidine kinase (HK) that senses an extracellular stimulus and a response regulator (RR) but can contain three or more proteins. Through gene duplication, a unique hybrid HK was created. We show that, while the hybrid appears to retain all of the phosphorelay functions, it responds to a different signal than the original. Both HKs transmit the signal to the same RR, which activates a promoter that transcribes a set of genes encoding a type III secretion system (T3SS) whose function is not yet evident. The significance of this work lies in finding that two HKs regulate this T3SS, highlighting its importance.
Funder
HHMI-BFW Medical Research Fellows Program
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
2 articles.
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