Affiliation:
1. Laboratoire d'Ingéniérie des Systèmes Macromoléculaires, UPR9027, IBSM/CNRS, 13402 Marseille Cedex 20, France,1 and
2. Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht,2 and
3. Genencor International B.V., 2300 AE Leiden,3 The Netherlands
Abstract
ABSTRACT
Pseudomonas aeruginosa
and
Pseudomonas alcaligenes
are gram-negative bacteria that secrete proteins using the type II or general secretory pathway, which requires at least 12
xcp
gene products (XcpA and XcpP to -Z). Despite strong conservation of this secretion pathway, gram-negative bacteria usually cannot secrete exoproteins from other species. Based on results obtained with
Erwinia
, it has been proposed that the XcpP and/or XcpQ homologs determine this secretion specificity (M. Linderberg, G. P. Salmond, and A. Collmer, Mol. Microbiol. 20:175–190, 1996). In the present study, we report that XcpP and XcpQ of
P. alcaligenes
could not substitute for their respective
P. aeruginosa
counterparts. However, these complementation failures could not be correlated to species-specific recognition of exoproteins, since these bacteria could secrete exoproteins of each other. Moreover, when
P. alcaligenes xcpP
and
xcpQ
were expressed simultaneously in a
P. aeruginosa xcpPQ
deletion mutant, complementation was observed, albeit only on agar plates and not in liquid cultures. After growth in liquid culture the heat-stable
P. alcaligenes
XcpQ multimers were not detected, whereas monomers were clearly visible. Together, our results indicate that the assembly of a functional Xcp machinery requires species-specific interactions between XcpP and XcpQ and between XcpP or XcpQ and another, as yet uncharacterized component(s).
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
30 articles.
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