scholarly journals Emerging Roles for NlpE as a Sensor for Lipoprotein Maturation and Transport to the Outer Membrane inEscherichia coli

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Brent W. Simpson ◽  
M. Stephen Trent
Keyword(s):  
Outer Membrane ◽  
Copper Stress ◽  
Gram Negative Bacteria ◽  
Two Component System ◽  
Inner Membrane ◽  
Complex Process ◽  
Outer Membrane Lipoprotein ◽  
Membrane Lipoprotein ◽  
Outer Membrane Biogenesis ◽  
Stress Pathway

ABSTRACTOuter membrane biogenesis is a complex process for Gram-negative bacteria as the components are synthesized in the cytoplasm or at the inner membrane and then transported to the outer membrane. Stress pathways monitor and respond to problems encountered in assembling the outer membrane. The two-component system CpxAR was recently reported to be a stress pathway for transport of lipoproteins to the outer membrane, but it was unclear how this stress is sensed. May et al. [K. L. May, K. M. Lehman, A. M. Mitchell, and M. Grabowicz, mBio 10(3):e00618-19, 2019,https://doi.org/10.1128/mBio.00618-19] determined that an outer membrane lipoprotein, NlpE, is the sensor for lipoprotein biogenesis stress. The group demonstrated that CpxAR is activated by the N-terminal domain of NlpE when the lipoprotein accumulates at the inner membrane. Further, this work resolved a previously debated role for NlpE in sensing copper stress; copper was shown to inhibit acylation of lipoproteins, preventing them from being transported to the outer membrane.

scholarly journals Inter-membrane association of the Sec and BAM translocons for bacterial outer-membrane biogenesis

2019 ◽  
Author(s):  
Sara Alvira ◽  
Daniel W. Watkins ◽  
Lucy Troman ◽  
William J. Allen ◽  
James Lorriman ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Conformational Changes ◽  
Major Constituent ◽  
Gram Negative Bacteria ◽  
Surface Adhesion ◽  
Core Complex ◽  
Inner Membrane ◽  
Bacterial Outer Membrane ◽  
Periplasmic Chaperones ◽  
Outer Membrane Biogenesis

SUMMARYThe outer-membrane of Gram-negative bacteria is critical for surface adhesion, pathogenicity, antibiotic resistance and survival. The major constituent – hydrophobic β-barrel Outer-Membrane Proteins (OMPs) – are secreted across the inner-membrane through the Sec-translocon for delivery to periplasmic chaperones e.g. SurA, which prevent aggregation. OMPs are then offloaded to the β-Barrel Assembly Machinery (BAM) in the outer-membrane for insertion and folding. We show the Holo-TransLocon (HTL: an assembly of the protein-channel core-complex SecYEG, the ancillary sub-complex SecDF, and the membrane ‘insertase’ YidC) contacts SurA and BAM through periplasmic domains of SecDF and YidC, ensuring efficient OMP maturation. Our results show the trans-membrane proton-motive-force (PMF) acts at distinct stages of protein secretion: for SecA-driven translocation across the inner-membrane through SecYEG; and to communicate conformational changes via SecDF to the BAM machinery. The latter presumably ensures efficient passage of OMPs. These interactions provide insights of inter-membrane organisation, the importance of which is becoming increasingly apparent.

scholarly journals Pal stabilises the bacterial outer membrane during constriction by a mobilisation-and-capture mechanism

2019 ◽  
Author(s):  
Joanna Szczepaniak ◽  
Peter Holmes ◽  
Karthik Rajasekar ◽  
Renata Kaminska ◽  
Firdaus Samsudin ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Outer Membrane Lipoprotein ◽  
Capture Mechanism ◽  
Dividing Cells ◽  
Bacterial Outer Membrane ◽  
Membrane Lipoprotein ◽  
Inner Membrane Protein

SummaryCoordination of outer membrane constriction with septation is critical to faithful division in Gram-negative bacteria and vital to the barrier function of the membrane. Recent studies suggest this coordination is through the active accumulation of the peptidoglycan-binding outer membrane lipoprotein Pal at division sites by the Tol system, but the mechanism is unknown. Here, we show that Pal accumulation at Escherichia coli division sites is a consequence of three key functions of the Tol system. First, Tol mobilises Pal molecules in dividing cells, which otherwise diffuse very slowly due to their binding of the cell wall. Second, Tol actively captures mobilised Pal molecules and deposits them at the division septum. Third, the active capture mechanism is analogous to that used by the inner membrane protein TonB to dislodge the plug domains of outer membrane TonB-dependent nutrient transporters. We conclude that outer membrane constriction is coordinated with cell division by active mobilisation-and-capture of Pal at division septa by the Tol system.

scholarly journals The Lipoprotein NlpE Is a Cpx Sensor That Serves as a Sentinel for Protein Sorting and Folding Defects in theEscherichia coliEnvelope

2019 ◽  
Vol 201 (10) ◽  
Author(s):  
Antoine Delhaye ◽  
Géraldine Laloux ◽  
Jean-François Collet
Keyword(s):  
Outer Membrane ◽  
Two Component System ◽  
Oxidative Folding ◽  
Component System ◽  
Content Type ◽  
E Coli ◽  
Outer Membrane Lipoprotein ◽  
Physiological Relevance ◽  
Two Component ◽  
Membrane Lipoprotein

ABSTRACTThe envelope of Gram-negative bacteria is a complex compartment that is essential for viability. To ensure survival of the bacterial cells in fluctuating environments, several signal transduction systems, called envelope stress response systems (ESRSs), exist to monitor envelope biogenesis and homeostasis. The Cpx two-component system is an extensively studied ESRS inEscherichia colithat is active during exposure to a vast array of stresses and protects the envelope under those harmful circumstances. Overproduction of NlpE, a two-domain outer membrane lipoprotein of unclear function, has been used in numerous studies as a molecular trigger to turn on the system artificially. However, the mechanism of Cpx activation by NlpE, as well as its physiological relevance, awaited further investigation. In this paper, we provide novel insights into the role played by NlpE in the Cpx system. We found that, among all outer membrane lipoproteins inE. coli, NlpE is sufficient to induce Cpx when lipoprotein trafficking is perturbed. Under such conditions, fitness is increased by the presence of NlpE. Moreover, we show that NlpE, through its N-terminal domain, physically interacts with the Cpx sensor kinase CpxA. Our data suggest that NlpE also serves to activate the Cpx system during oxidative folding defects in the periplasm and that its C-terminal domain is involved in the sensing mechanism. Overall, our data demonstrate that NlpE acts as a sentinel for two important envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding, and they further establish NlpE as a bona fide member of the Cpx two-component system.IMPORTANCEBacteria rely on a sophisticated envelope to shield them against challenging environmental conditions and therefore need to ensure correct envelope assembly and integrity. A major signaling pathway that performs this role in Gram-negative species is the Cpx system. An outer membrane lipoprotein of unclear function, NlpE, has long been exploited as a research tool to study Cpx inE. coli, since it triggers this system when overproduced or mislocalized; however, the mechanism and physiological relevance of the NlpE-Cpx connection have awaited further investigation. We elucidate a new function for NlpE by showing that it physically interacts with the Cpx sensor CpxA and acts as a sentinel that specifically monitors two essential envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding.

scholarly journals Inter-membrane association of the Sec and BAM translocons for bacterial outer-membrane biogenesis

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Sara Alvira ◽  
Daniel W Watkins ◽  
Lucy Troman ◽  
William J Allen ◽  
James S Lorriman ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Conformational Changes ◽  
Major Constituent ◽  
Gram Negative Bacteria ◽  
Surface Adhesion ◽  
Core Complex ◽  
Inner Membrane ◽  
Bacterial Outer Membrane ◽  
Periplasmic Chaperones ◽  
Outer Membrane Biogenesis

The outer-membrane of Gram-negative bacteria is critical for surface adhesion, pathogenicity, antibiotic resistance and survival. The major constituent – hydrophobic β-barrel Outer-Membrane Proteins (OMPs) – are first secreted across the inner-membrane through the Sec-translocon for delivery to periplasmic chaperones, for example SurA, which prevent aggregation. OMPs are then offloaded to the β-Barrel Assembly Machinery (BAM) in the outer-membrane for insertion and folding. We show the Holo-TransLocon (HTL) – an assembly of the protein-channel core-complex SecYEG, the ancillary sub-complex SecDF, and the membrane ‘insertase’ YidC – contacts BAM through periplasmic domains of SecDF and YidC, ensuring efficient OMP maturation. Furthermore, the proton-motive force (PMF) across the inner-membrane acts at distinct stages of protein secretion: (1) SecA-driven translocation through SecYEG and (2) communication of conformational changes via SecDF across the periplasm to BAM. The latter presumably drives efficient passage of OMPs. These interactions provide insights of inter-membrane organisation and communication, the importance of which is becoming increasingly apparent.

scholarly journals Deletion of lolB, Encoding an Outer Membrane Lipoprotein, Is Lethal for Escherichia coli and Causes Accumulation of Lipoprotein Localization Intermediates in the Periplasm

2001 ◽  
Vol 183 (22) ◽  
pp. 6538-6542 ◽  
Author(s):  
Kimie Tanaka ◽  
Shin-Ichi Matsuyama ◽  
Hajime Tokuda
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Temperature Sensitive ◽  
Helper Plasmid ◽  
Inner Membrane ◽  
Outer Membrane Lipoprotein ◽  
Lipoprotein Complex ◽  
Membrane Lipoprotein

ABSTRACT Outer membrane lipoproteins of Escherichia coli are released from the inner membrane upon the formation of a complex with a periplasmic chaperone, LolA, followed by localization to the outer membrane. In vitro biochemical analyses revealed that the localization of lipoproteins to the outer membrane generally requires an outer membrane lipoprotein, LolB, and occurs via transient formation of a LolB-lipoprotein complex. On the other hand, a mutant carrying the chromosomal lolB gene under the control of thelac promoter-operator grew normally in the absence of LolB induction if the mutant did not possess the major outer membrane lipoprotein Lpp, suggesting that LolB is only important for the localization of Lpp in vivo. To examine the in vivo function of LolB, we constructed a chromosomal lolB null mutant harboring a temperature-sensitive helper plasmid carrying the lolBgene. At a nonpermissive temperature, depletion of the LolB protein due to loss of the lolB gene caused cessation of growth and a decrease in the number of viable cells irrespective of the presence or absence of Lpp. LolB-depleted cells accumulated the LolA-lipoprotein complex in the periplasm and the mature form of lipoproteins in the inner membrane. Taken together, these results indicate that LolB is the first example of an essential lipoprotein for E. coliand that its depletion inhibits the upstream reactions of lipoprotein trafficking.

Sign in / Sign up

Export Citation Format

Share Document