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J. Bacteriol., Aug 1996, 4997-5004, Vol 178, No. 16
MJ Schurr, H Yu, JM Martinez-Salazar, JC Boucher and V Deretic
The alternative sigma factor AlgU (Pseudomonas aeruginosa sigma E) is
required for full resistance of P. aeruginosa to oxidative stress and
extreme temperatures. AlgU also controls conversion of P. aeruginosa to the
mucoid, alginate-overproducing phenotype associated with lethal infections
in cystic fibrosis patients. Mutations that cause conversion to mucoidy in
cystic fibrosis isolates occur frequently in mucA, the second gene within
the algU mucABCD gene cluster. Here we analyze the biochemical basis of
conversion to mucoidy. MucA was shown to act as an anti-sigma factor by
binding to AlgU and inhibiting its activity. MucB, another negative
regulator of AlgU, was localized in the periplasm. MucB exerts its function
from this compartment, since deletion of the leader peptide and the
cytoplasmic location of MucB abrogated its ability to inhibit mucoidy.
These data support a model in which a multicomponent system, encompassing
an anti-delta factor and elements in the periplasmic compartment, modulates
activity of AlgU. Since factors controlling AlgU are conserved in other
gram-negative bacteria, the processes controlling conversion to mucoidy in
P. aeruginosa may be applicable to the regulation of AlgU (sigma E)
equivalents in other organisms.
Copyright © 1996, American Society for Microbiology
Control of AlgU, a member of the sigma E-like family of stress sigma factors, by the negative regulators MucA and MucB and Pseudomonas aeruginosa conversion to mucoidy in cystic fibrosis
Department of Microbiology, University of Texas Health Science Center at San Antonio 78284-7758, USA.
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