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Journal of Bacteriology, January 2001, p. 587-596, Vol. 183, No. 2
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

Andreas Urban, Martina Leipelt,dagger Thorsten Eggert, and Karl-Erich Jaeger*

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.

* 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.

dagger Present address: Institute für Allgemeine Botanik, Universität Hamburg, D-22609 Hamburg, Germany.

Journal of Bacteriology, January 2001, p. 587-596, Vol. 183, No. 2
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.2.587-596.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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