scholarly journals Association of Escherichia coli ribosomes with the inner membrane requires the signal recognition particle receptor but is independent of the signal recognition particle

2000 ◽  
Vol 97 (9) ◽  
pp. 4621-4626 ◽  
Author(s):  
A. A. Herskovits ◽  
E. Bibi
Keyword(s):  
Escherichia Coli ◽  
Signal Recognition Particle ◽  
Signal Recognition ◽  
Inner Membrane ◽  
Signal Recognition Particle Receptor

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 Translocation of α-Synuclein Expressed in Escherichia coli

2007 ◽  
Vol 189 (7) ◽  
pp. 2777-2786 ◽  
Author(s):  
Guoping Ren ◽  
Xi Wang ◽  
Shufeng Hao ◽  
Hongyu Hu ◽  
Chih-chen Wang
Keyword(s):  
Escherichia Coli ◽  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Signal Sequence ◽  
Signal Recognition Particle ◽  
Lewy Bodies ◽  
Signal Recognition ◽  
Inner Membrane ◽  
Dependent Pathway

ABSTRACT α-Synuclein is a major component of Lewy bodies in Parkinson's disease. Although no signal sequence is apparent, α-synuclein expressed in Escherichia coli is mostly located in the periplasm. The possibilities that α-synuclein translocated into the periplasm across the inner membrane by the SecA or the Tat targeting route identified in bacteria and that α-synuclein was released through MscL were excluded. The signal recognition particle-dependent pathway is involved in the translocation of α-synuclein. The C-terminal 99-to-140 portion of the α-synuclein molecule plays a signal-like role for its translocation into the periplasm, cooperating with the central 61-to-95 section. The N-terminal 1-to-60 region is not required for this translocation.

scholarly journals Physiological Basis for Conservation of the Signal Recognition Particle Targeting Pathway in Escherichia coli

2001 ◽  
Vol 183 (7) ◽  
pp. 2187-2197 ◽  
Author(s):  
Harris D. Bernstein ◽  
Janine B. Hyndman
Keyword(s):  
Escherichia Coli ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Signal Recognition Particle ◽  
Growth Conditions ◽  
Signal Recognition ◽  
Physiological Basis ◽  
Inner Membrane ◽  
Shock Response ◽  
Shock Proteins

ABSTRACT The Escherichia coli signal recognition particle (SRP) is a ribonucleoprotein complex that targets nascent inner membrane proteins (IMPs) to transport sites in the inner membrane (IM). Since SRP depletion only partially inhibits IMP insertion under some growth conditions, however, it is not clear why the particle is absolutely essential for viability. Insights into this question emerged from experiments in which we analyzed the physiological consequences of reducing the intracellular concentration of SRP below the wild-type level. We found that even moderate SRP deficiencies that have little effect on cell growth led to the induction of a heat shock response. Genetic manipulations that suppress the heat shock response were lethal in SRP-deficient cells, indicating that the elevated synthesis of heat shock proteins plays an important role in maintaining cell viability. Although it is conceivable that the heat shock response serves to increase the capacity of cells to target IMPs via chaperone-based mechanisms, SRP-deficient cells did not show an increased dependence on either GroEL or DnaK. By contrast, the heat shock-regulated proteases Lon and ClpQ became essential for viability when SRP levels were reduced. These results suggest that the heat shock response protects SRP-deficient cells by increasing their capacity to degrade mislocalized IMPs. Consistent with this notion, a model IMP that was mislocalized in the cytoplasm as the result of SRP depletion appeared to be more stable in a Δlon ΔclpQ strain than in control cells. Taken together, the data provide direct evidence that SRP is essential in E. coli and possibly conserved throughout prokaryotic evolution as well partly because efficient IMP targeting prevents a toxic accumulation of aggregated proteins in the cytoplasm.

scholarly journals The Core Escherichia coli Signal Recognition Particle Receptor Contains Only the N and G Domains of FtsY

2004 ◽  
Vol 186 (8) ◽  
pp. 2492-2494 ◽  
Author(s):  
Asa Eitan ◽  
Eitan Bibi
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Signal Recognition Particle ◽  
Membrane Targeting ◽  
Signal Recognition ◽  
Amino Acid Residues ◽  
The Core ◽  
Signal Recognition Particle Receptor

ABSTRACT Previous studies have proposed that the N-terminal A domain (∼200 amino acid residues) of the Escherichia coli signal recognition particle (SRP) receptor, FtsY, is required for membrane targeting. In contrast to this suggestion, we show that A domain-truncated versions of FtsY, harboring only domains N and G, are functional. Therefore, we propose that N and G domains constitute the core SRP receptor.

Assembly strategies and GTPase regulation of the eukaryotic and Escherichia coli translocons

2001 ◽  
Vol 79 (5) ◽  
pp. 593-601 ◽  
Author(s):  
Kyle R Legate ◽  
David W Andrews
Keyword(s):  
Escherichia Coli ◽  
Endoplasmic Reticulum ◽  
Protein Translocation ◽  
Signal Recognition Particle ◽  
The Novel ◽  
Signal Recognition ◽  
Inner Membrane ◽  
Membrane Bound

The translocation of most proteins across the endoplasmic reticulum or bacterial inner membrane occurs through an aqueous pore that spans the membrane. Substrates that are translocated co-translationally across the membrane are directed to the translocation pore via an interaction between the cytosolic signal recognition particle and its membrane-bound receptor. Together the translocation pore and the receptor are referred to as a translocon. By studying the biogenesis of the translocon a number of alternate targeting and membrane-integration pathways have been discovered that operate independently of the signal recognition particle (SRP) pathway. The novel assembly strategies of the translocon and the ways in which these components interact to ensure the fidelity and unidirectionality of the targeting and translocation process are reviewed here.Key words: protein translocation, translocon, SRP receptor, GTPases.

scholarly journals The Structure of Multiple Polypeptide Domains Determines the Signal Recognition Particle Targeting Requirement ofEscherichia coli Inner Membrane Proteins

1999 ◽  
Vol 181 (15) ◽  
pp. 4561-4567 ◽  
Author(s):  
John A. Newitt ◽  
Nancy D. Ulbrandt ◽  
Harris D. Bernstein
Keyword(s):  
Escherichia Coli ◽  
Alkaline Phosphatase ◽  
Membrane Proteins ◽  
Signal Recognition Particle ◽  
Protein Export ◽  
Signal Recognition ◽  
Inner Membrane ◽  
Periplasmic Domain ◽  
Membrane Spanning ◽  
Membrane Spanning Domains

ABSTRACT The signal recognition particle (SRP) targeting pathway is required for the efficient insertion of many polytopic inner membrane proteins (IMPs) into the Escherichia coli inner membrane, but in the absence of SRP protein export proceeds normally. To define the properties of IMPs that impose SRP dependence, we analyzed the targeting requirements of bitopic IMPs that are structurally intermediate between exported proteins and polytopic IMPs. We found that disruption of the SRP pathway inhibited the insertion of only a subset of bitopic IMPs. Studies on a model bitopic AcrB-alkaline phosphatase fusion protein (AcrB 265-AP) showed that the SRP requirement for efficient insertion correlated with the presence of a large periplasmic domain (P1). As previously reported, perturbation of the SRP pathway also affected the insertion of a polytopic AcrB-AP fusion. Even exhaustive SRP depletion, however, failed to block the insertion of any AcrB derivative by more than 50%. Taken together, these data suggest that many proteins that are normally targeted by SRP can utilize alternative targeting pathways and that the structure of both hydrophilic and membrane-spanning domains determines the degree to which the biogenesis of a protein is SRP dependent.

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