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Journal of Bacteriology, February 2001, p. 1312-1319, Vol. 183, No. 4
Unité de Génétique
Moléculaire, CNRS URA 1773-Institut Pasteur, 75724 Paris Cedex
15, France
Received 12 July 2000/Accepted 15 November 2000
When expressed in Escherichia coli, the 15 Klebsiella oxytoca pul genes that encode the so-called Pul
secreton or type II secretion machinery promote pullulanase secretion
and the assembly of one of the secreton components, PulG, into pili.
Besides these pul genes, efficient pullulanase secretion
also requires the host dsbA gene, encoding a periplasmic
disulfide oxidoreductase, independently of disulfide bond formation in
pullulanase itself. Two secreton components, the secretin pilot protein
PulS and the minor pseudopilin PulK, were each shown to posses an
intramolecular disulfide bond whose formation was catalyzed by DsbA.
PulS was apparently destabilized by the absence of its disulfide bond,
whereas PulK stability was not dramatically affected either by a
dsbA mutation or by the removal of one of its cysteines.
The pullulanase secretion defect in a dsbA mutant was
rectified by overproduction of PulK, indicating reduced disulfide bond
formation in PulK as the major cause of the secretion defect under the
conditions tested (in which PulS is probably present in considerable
excess of requirements). PulG pilus formation was independent of DsbA,
probably because PulK is not needed for piliation.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.4.1312-1319.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Disulfide Bond Formation in Secreton Component PulK
Provides a Possible Explanation for the Role of DsbA in
Pullulanase Secretion
*
Corresponding author. Mailing address: Unité de
Génétique moléculaire, Institut Pasteur, 25, rue du
Dr. Roux, 75724 Paris CEDEX 15, France. Phone: 33/0-145688494. Fax:
33/0-145688960. E-mail: max{at}pasteur.fr.
Present address: Microbial Pathogenesis Unit,
Université Catholique de Louvain, B-1200 Brussels, Belgium.
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