Affiliation:
1. Department of Life Science and Institute of Molecular Medicine, National Tsing Hua University
2. Department of Biological Science and Technology, National Chiao Tung University, Hsin Chu, Taiwan, Republic of China
Abstract
ABSTRACT
The
rmpA2
gene, which encodes an activator for capsular polysaccharide (CPS) synthesis, was isolated from a 200-kb virulence plasmid of
Klebsiella pneumoniae
CG43. Based on the sequence homology with LuxR at the carboxyl-terminal DNA-binding motif, we hypothesized that RmpA2 exerts its effect by activating the expression of
cps
genes that are responsible for CPS biosynthesis. Two
luxAB
transcriptional fusions, each containing a putative promoter region of the
K. pneumoniae
K2
cps
genes, were constructed and were found to be activated in the presence of multicopy
rmpA2
. The activation is likely due to direct binding of RmpA2 to the
cps
gene promoter through its C-terminal DNA binding motif. Moreover, the loss of colony mucoidy in a
K. pneumoniae
strain deficient in RcsB, a regulator for
cps
gene expression, could be recovered by complementing the strain with a multicopy plasmid carrying
rmpA2
. The CPS production in Lon protease-deficient
K. pneumoniae
significantly increased, and the effect was accompanied by an increase of RmpA2 stability. The expression of the
rmpA2
gene was negatively autoregulated and could be activated when the organism was grown in M9 minimal medium. An IS
3
element located upstream of the
rmpA2
was required for the full activation of the
rmpA2
promoter. In summary, our results suggest that the enhancement of K2 CPS synthesis in
K. pneumoniae
CG43 by RmpA2 can be attributed to its transcriptional activation of K2
cps
genes, and the expression level of
rmpA2
is autoregulated and under the control of Lon protease.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
120 articles.
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