scholarly journals Inner membrane proteins YgdD and SbmA are required for the complete susceptibility of Escherichia coli to the proline-rich antimicrobial peptide arasin 1(1–25)

Microbiology ◽  
2016 ◽  
Vol 162 (4) ◽  
pp. 601-609 ◽  
Author(s):  
Victoria S. Paulsen ◽  
Mario Mardirossian ◽  
Hans-Matti Blencke ◽  
Monica Benincasa ◽  
Giulia Runti ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Antimicrobial Peptide ◽  
Inner Membrane

scholarly journals Dissecting the Translocase and Integrase Functions of the Escherichia coli Secyeg Translocon

2000 ◽  
Vol 150 (3) ◽  
pp. 689-694 ◽  
Author(s):  
Hans-Georg Koch ◽  
Matthias Müller
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Protein Delivery ◽  
Signal Recognition Particle ◽  
Membrane Vesicles ◽  
Biologically Active ◽  
Secretory Proteins ◽  
Signal Recognition ◽  
Inner Membrane ◽  
Independent Protein

Recent evidence suggests that in Escherichia coli, SecA/SecB and signal recognition particle (SRP) are constituents of two different pathways targeting secretory and inner membrane proteins to the SecYEG translocon of the plasma membrane. We now show that a secY mutation, which compromises a functional SecY–SecA interaction, does not impair the SRP-mediated integration of polytopic inner membrane proteins. Furthermore, under conditions in which the translocation of secretory proteins is strictly dependent on SecG for assisting SecA, the absence of SecG still allows polytopic membrane proteins to integrate at the wild-type level. These results indicate that SRP-dependent integration and SecA/SecB-mediated translocation do not only represent two independent protein delivery systems, but also remain mechanistically distinct processes even at the level of the membrane where they engage different domains of SecY and different components of the translocon. In addition, the experimental setup used here enabled us to demonstrate that SRP-dependent integration of a multispanning protein into membrane vesicles leads to a biologically active enzyme.

scholarly journals Tail-Anchored Inner Membrane Protein ElaB Increases Resistance to Stress While Reducing Persistence in Escherichia coli

2017 ◽  
Vol 199 (9) ◽  
Author(s):  
Yunxue Guo ◽  
Xiaoxiao Liu ◽  
Baiyuan Li ◽  
Jianyun Yao ◽  
Thomas K. Wood ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Stationary Phase ◽  
Transmembrane Domain ◽  
Inner Membrane ◽  
Content Type ◽  
E Coli ◽  
Inner Membrane Protein

ABSTRACT Host-associated bacteria, such as Escherichia coli, often encounter various host-related stresses, such as nutritional deprivation, oxidative stress, and temperature shifts. There is growing interest in searching for small endogenous proteins that mediate stress responses. Here, we characterized the small C-tail-anchored inner membrane protein ElaB in E. coli. ElaB belongs to a class of tail-anchored inner membrane proteins with a C-terminal transmembrane domain but lacking an N-terminal signal sequence for membrane targeting. Proteins from this family have been shown to play vital roles, such as in membrane trafficking and apoptosis, in eukaryotes; however, their role in prokaryotes is largely unexplored. Here, we found that the transcription of elaB is induced in the stationary phase in E. coli and stationary-phase sigma factor RpoS regulates elaB transcription by binding to the promoter of elaB. Moreover, ElaB protects cells against oxidative stress and heat shock stress. However, unlike membrane peptide toxins TisB and GhoT, ElaB does not lead to cell death, and the deletion of elaB greatly increases persister cell formation. Therefore, we demonstrate that disruption of C-tail-anchored inner membrane proteins can reduce stress resistance; it can also lead to deleterious effects, such as increased persistence, in E. coli. IMPORTANCE Escherichia coli synthesizes dozens of poorly understood small membrane proteins containing a predicted transmembrane domain. In this study, we characterized the function of the C-tail-anchored inner membrane protein ElaB in E. coli. ElaB increases resistance to oxidative stress and heat stress, while inactivation of ElaB leads to high persister cell formation. We also demonstrated that the transcription of elaB is under the direct regulation of stationary-phase sigma factor RpoS. Thus, our study reveals that small inner membrane proteins may have important cellular roles during the stress response.

scholarly journals Defects in The First Step of Lipoprotein Maturation Underlie The Synthetic Lethality of Escherichia coli Lacking The Inner Membrane Proteins YciB And DcrB

2021 ◽  
Author(s):  
Aaron Mychack ◽  
Anuradha Janakiraman
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Membrane Fluidity ◽  
Double Mutant ◽  
Synthetic Lethality ◽  
Cell Envelope ◽  
Initial Step ◽  
Inner Membrane ◽  
E Coli ◽  
Membrane Lipoprotein

Nearly a quarter of the Escherichia coli genome encodes for inner membrane proteins of which approximately a third have unassigned or poorly understood function. We had previously demonstrated that the synergy between the functional roles of the inner membrane-spanning YciB and the inner membrane lipoprotein DcrB, is essential in maintaining cell envelope integrity. In yciB dcrB cells, the abundant outer membrane lipoprotein, Lpp, mislocalizes to the inner membrane where it forms toxic linkages to peptidoglycan. Here, we report that the aberrant localization of Lpp in this double mutant is due to inefficient lipid modification at the first step in lipoprotein maturation. Both Cpx and Rcs signaling systems are upregulated in response to the envelope stress. The phosphatidylglycerol-pre-prolipoprotein diacylglyceryl transferase, Lgt, catalyzes the initial step in lipoprotein maturation. Our results suggest that the attenuation in Lgt-mediated transacylation in the double mutant is not a consequence of lowered phosphatidylglycerol levels. Instead, we posit that altered membrane fluidity, perhaps due to changes in lipid homeostasis, may lead to the impairment in Lgt function. Consistent with this idea, a dcrB null is not viable when grown at low temperatures, conditions which impact membrane fluidity. Like the yciB dcrB double mutant, dcrB null-mediated toxicity can be overcome in distinct ways - by increased expression of Lgt, deletion of lpp, or removal of Lpp-peptidoglycan linkages. The last of these events leads to elevated membrane vesiculation and lipid loss, which may, in turn, impact membrane homeostasis in the double mutant. Importance A distinguishing feature of Gram-negative bacteria is their double-membraned cell envelope which presents a formidable barrier against environmental stress. In E. coli, more than a quarter of the cellular proteins reside at the inner membrane but about a third of these proteins are functionally unassigned or their function is incompletely understood. Here, we show that the synthetic lethality underlying the inactivation of two inner membrane proteins, a small integral membrane protein YciB, and a lipoprotein, DcrB, results from the attenuation of the first step of lipoprotein maturation at the inner membrane. We propose that these two inner membrane proteins YciB and DcrB play a role in membrane homeostasis in E. coli and related bacteria.

scholarly journals Effects of SecE Depletion on the Inner and Outer Membrane Proteomes of Escherichia coli

2008 ◽  
Vol 190 (10) ◽  
pp. 3505-3525 ◽  
Author(s):  
Louise Baars ◽  
Samuel Wagner ◽  
David Wickström ◽  
Mirjam Klepsch ◽  
A. Jimmy Ytterberg ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Protein Identification ◽  
Protein Translocation ◽  
Outer Membrane Proteins ◽  
Specific Model ◽  
Secretory Proteins ◽  
Inner Membrane ◽  
Sec Translocon

ABSTRACT The Sec translocon is a protein-conducting channel that allows polypeptides to be transferred across or integrated into a membrane. Although protein translocation and insertion in Escherichia coli have been studied using only a small set of specific model substrates, it is generally assumed that most secretory proteins and inner membrane proteins use the Sec translocon. Therefore, we have studied the role of the Sec translocon using subproteome analysis of cells depleted of the essential translocon component SecE. The steady-state proteomes and the proteome dynamics were evaluated using one- and two-dimensional gel analysis, followed by mass spectrometry-based protein identification and extensive immunoblotting. The analysis showed that upon SecE depletion (i) secretory proteins aggregated in the cytoplasm and the cytoplasmic σ32 stress response was induced, (ii) the accumulation of outer membrane proteins was reduced, with the exception of OmpA, Pal, and FadL, and (iii) the accumulation of a surprisingly large number of inner membrane proteins appeared to be unaffected or increased. These proteins lacked large translocated domains and/or consisted of only one or two transmembrane segments. Our study suggests that several secretory and inner membrane proteins can use Sec translocon-independent pathways or have superior access to the remaining Sec translocons present in SecE-depleted cells.

Assembly of Inner Membrane Proteins in Escherichia Coli

2003 ◽  
pp. 65-82
Author(s):  
David Drew ◽  
Linda Fröderberg ◽  
Louise Baars ◽  
Joen Luirink ◽  
Jan-Willem de Gier
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Inner Membrane

scholarly journals Temperature Sensitivity and Cell Division Defects in an Escherichia coli Strain with Mutations in yghB and yqjA, Encoding Related and Conserved Inner Membrane Proteins

2008 ◽  
Vol 190 (13) ◽  
pp. 4489-4500 ◽  
Author(s):  
Kandi Thompkins ◽  
Ballari Chattopadhyay ◽  
Ying Xiao ◽  
Margaret C. Henk ◽  
William T. Doerrler
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Membrane Proteins ◽  
Elevated Temperatures ◽  
Divalent Cations ◽  
Microscopic Analysis ◽  
Coli Strain ◽  
Temperature Sensitive ◽  
Membrane Composition ◽  
Inner Membrane

ABSTRACT Ludox density gradients were used to enrich for Escherichia coli mutants with conditional growth defects and alterations in membrane composition. A temperature-sensitive mutant named Lud135 was isolated with mutations in two related, nonessential genes: yghB and yqjA. yghB harbors a single missense mutation (G203D) and yqjA contains a nonsense mutation (W92TGA) in Lud135. Both mutations are required for the temperature-sensitive phenotype: targeted deletion of both genes in a wild-type background results in a strain with a similar phenotype and expression of either gene from a plasmid restores growth at elevated temperatures. The mutant has altered membrane phospholipid levels, with elevated levels of acidic phospholipids, when grown under permissive conditions. Growth of Lud135 under nonpermissive conditions is restored by the presence of millimolar concentrations of divalent cations Ca2+, Ba2+, Sr2+, or Mg2+ or 300 to 500 mM NaCl but not 400 mM sucrose. Microscopic analysis of Lud135 demonstrates a dramatic defect at a late stage of cell division when cells are grown under permissive conditions. yghB and yqjA belong to the conserved and widely distributed dedA gene family, for which no function has been reported. The two open reading frames encode predicted polytopic inner membrane proteins with 61% amino acid identity. It is likely that YghB and YqjA play redundant but critical roles in membrane biology that are essential for completion of cell division in E. coli.

scholarly journals Insertion of a MalE β-Galactosidase Fusion Protein into the Envelope of Escherichia coli Disrupts Biogenesis of Outer Membrane Proteins and Processing of Inner Membrane Proteins

1982 ◽  
Vol 152 (1) ◽  
pp. 133-139
Author(s):  
Enrique Herrero ◽  
Maria Jackson ◽  
Phillip J. Bassford ◽  
David Sinden ◽  
I. Barry Holland
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Signal Sequence ◽  
Relative Rate ◽  
Outer Membrane Proteins ◽  
Limiting Factor ◽  
Hybrid Protein ◽  
Inner Membrane ◽  
Reduced Rate

The synthesis of a membrane-bound MalE β-galactosidase hybrid protein, when induced by growth of Escherichia coli on maltose, leads to inhibition of cell division and eventually a reduced rate of mass increase. In addition, the relative rate of synthesis of outer membrane proteins, but not that of inner membrane proteins, was reduced by about 50%. Kinetic experiments demonstrated that this reduction coincided with the period of maximum synthesis of the hybrid protein (and another maltose-inducible protein, LamB). The accumulation of this abnormal protein in the envelope therefore appeared specifically to inhibit the synthesis, the assembly of outer membrane proteins, or both, indicating that the hybrid protein blocks some export site or causes the sequestration of some limiting factor(s) involved in the export process. Since the MalE protein is normally located in the periplasm, the results also suggest that the synthesis of periplasmic and outer membrane proteins may involve some steps in common. The reduced rate of synthesis of outer membrane proteins was also accompanied by the accumulation in the envelope of at least one outer membrane protein and at least two inner membrane proteins as higher-molecular-weight forms, indicating that processing (removal of the N-terminal signal sequence) was also disrupted by the presence of the hybrid protein. These results may indicate that the assembly of these membrane proteins is blocked at a relatively late step rather than at the level of primary recognition of some site by the signal sequence. In addition, the results suggest that some step common to the biogenesis of quite different kinds of envelope protein is blocked by the presence of the hybrid protein.

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