13117
2013
eng
e55010
1
8
article
1
2016-04-01
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Identification and Characterization of a Novel Porin Family Highlights a Major Difference in the Outer Membrane of Chlamydial Symbionts and Pathogens
The Chlamydiae constitute an evolutionary well separated group of intracellular bacteria comprising important pathogens of humans as well as symbionts of protozoa. The amoeba symbiont Protochlamydia amoebophila lacks a homologue of the most abundant outer membrane protein of the Chlamydiaceae, the major outer membrane protein MOMP, highlighting a major difference between environmental chlamydiae and their pathogenic counterparts. We recently identified a novel family of putative porins encoded in the genome of P. amoebophila by in silico analysis. Two of these Protochlamydia outer membrane proteins, PomS (pc1489) and PomT (pc1077), are highly abundant in outer membrane preparations of this organism. Here we show that all four members of this putative porin family are toxic when expressed in the heterologous host Escherichia coli. Immunofluorescence analysis using antibodies against heterologously expressed PomT and PomS purified directly from elementary bodies, respectively, demonstrated the location of both proteins in the outer membrane of P. amoebophila. The location of the most abundant protein PomS was further confirmed by immuno-transmission electron microscopy. We could show that pomS is transcribed, and the corresponding protein is present in the outer membrane throughout the complete developmental cycle, suggesting an essential role for P. amoebophila. Lipid bilayer measurements demonstrated that PomS functions as a porin with anion-selectivity and a pore size similar to the Chlamydiaceae MOMP. Taken together, our results suggest that PomS, possibly in concert with PomT and other members of this porin family, is the functional equivalent of MOMP in P. amoebophila. This work contributes to our understanding of the adaptations of symbiotic and pathogenic chlamydiae to their different eukaryotic hosts.
PLoS ONE
10.1371/journal.pone.0055010
urn:nbn:de:bvb:20-opus-131176
PLoS ONE 8(1): e55010. doi:10.1371/journal.pone.0055010
Karin Aistleitner
Christian Heinz
Alexandra Hoermann
Eva Heinz
Jacqueline Montanaro
Frederik Schulz
Elke Maier
Peter Pichler
Roland Benz
Matthias Horn
eng
uncontrolled
cell wall
eng
uncontrolled
protochlamydia amoebophila
eng
uncontrolled
escherichia coli
eng
uncontrolled
matrix protein porin
eng
uncontrolled
gram negative bacteria
eng
uncontrolled
single channel analysis
eng
uncontrolled
developmental cycle
eng
uncontrolled
mycobacterium smegmatis
eng
uncontrolled
monoclonal antibodies
eng
uncontrolled
signal peptides
Medizin und Gesundheit
open_access
Rudolf-Virchow-Zentrum
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/13117/097_Aistleitner_Plos_One.pdf
14511
2015
eng
e0143557
11
10
article
1
2017-03-02
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OmpW of Caulobacter crescentus functions as an outer membrane channel for cations
Caulobacter crescentus is an oligotrophic bacterium that lives in dilute organic environments such as soil and freshwater. This bacterium represents an interesting model for cellular differentiation and regulation because daughter cells after division have different forms: one is motile while the other is non-motile and can adhere to surfaces. Interestingly, the known genome of C. crescentus does not contain genes predicted to code for outer membrane porins of the OmpF/C general diffusion type present in enteric bacteria or those coding for specific porins selective for classes of substrates. Instead, genes coding for 67 TonB-dependent outer membrane receptors have been identified, suggesting that active transport of specific nutrients may be the norm. Here, we report that high channel-forming activity was observed with crude outer membrane extracts of C. crescentus in lipid bilayer experiments, indicating that the outer membrane of C. crescentus contained an ion-permeable channel with a single-channel conductance of about 120 pS in 1M KCl. The channel-forming protein with an apparent molecular mass of about 20 kDa was purified to homogeneity. Partial protein sequencing of the protein indicated it was a member of the OmpW family of outer membrane proteins from Gram-negative bacteria. This channel was not observed in reconstitution experiments with crude outer membrane extracts of an OmpW deficient C. crescentus mutant. Biophysical analysis of the C. crescentus OmpW suggested that it has features that are special for general diffusion porins of Gram-negative outer membranes because it was not a wide aqueous channel. Furthermore, OmpW of C. crescentus seems to be different to known OmpW porins and has a preference for ions, in particular cations. A putative model for OmpW of C. crescentus was built on the basis of the known 3D-structures of OmpW of Escherichia coli and OprG of Pseudomonas aeruginosa using homology modeling. A comparison of the two known structures with the model of OmpW of C. crescentus suggested that it has a more hydrophilic interior and possibly a larger diameter.
PLoS ONE
10.1371/journal.pone.0143557
urn:nbn:de:bvb:20-opus-145114
PLoS ONE 10(11): e0143557 (2015). DOI: 10.1371/journal.pone.0143557
FP7/2007-2013
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Roland Benz
Michael D. Jones
Farhan Younas
Elke Maier
Niraj Modi
Reinhard Mentele
Friedrich Lottspeich
Ulrich Kleinekathöfer
John Smit
eng
uncontrolled
matrix protein porin
eng
uncontrolled
amino acid sequence
eng
uncontrolled
escherichia coli
eng
uncontrolled
selective channel
eng
uncontrolled
molecular basis
eng
uncontrolled
lipid bilayer membranes
eng
uncontrolled
S-layer protein
eng
uncontrolled
pseudomonas aeruginosa
eng
uncontrolled
ionic selectivity
eng
uncontrolled
cell wall
Medizin und Gesundheit
open_access
Rudolf-Virchow-Zentrum
OpenAIRE
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/14511/089_Benz_PLoS_ONE.PDF