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Journal of Bacteriology, January 2001, p. 587-596, Vol. 183, No. 2
Lehrstuhl für Biologie der
Mikroorganismen, Ruhr-Universität Bochum, D-44780 Bochum,
Germany
Received 20 March 2000/Accepted 19 October 2000
DsbA and DsbC proteins involved in the periplasmic formation of
disulfide bonds in Pseudomonas aeruginosa were identified and shown to play an important role for the formation of extracellular enzymes. Mutants deficient in either dsbA or
dsbC or both genes were constructed, and extracellular
elastase, alkaline phosphatase, and lipase activities were determined.
The dsbA mutant no longer produced these enzymes, whereas
the lipase activity was doubled in the dsbC mutant. Also,
extracellar lipase production was severely reduced in a P. aeruginosa dsbA mutant in which an inactive DsbA variant carrying
the mutation C34S was expressed. Even when the lipase gene
lipA was constitutively expressed in trans in a
lipA dsbA double mutant, lipase activity in cell extracts
and culture supernatants was still reduced to about 25%.
Interestingly, the presence of dithiothreitol in the growth medium
completely inhibited the formation of extracellular lipase whereas the
addition of dithiothreitol to a cell-free culture supernatant did not
affect lipase activity. We conclude that the correct formation of the disulfide bond catalyzed in vivo by DsbA is necessary to stabilize periplasmic lipase. Such a stabilization is the prerequisite for efficient secretion using the type II pathway.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.2.587-596.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
DsbA and DsbC Affect Extracellular Enzyme Formation
in Pseudomonas aeruginosa

*
Corresponding author. Mailing address: Lehrstuhl
für Biologie der Mikroorganismen, Ruhr-Universität Bochum,
Universitätsstrasse 150, D-44780 Bochum, Germany. Phone: (49) 234 322-3101. Fax: (49) 234 321-4425. E-mail:
karl-erich.jaeger{at}ruhr-uni-bochum.de.
Present address: Institute für Allgemeine Botanik,
Universität Hamburg, D-22609 Hamburg, Germany.
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