This title appears in the Scientific Report :
2012
Untersuchungen zur Membranintegrität während der Tat-abhängigen Proteintranslokation in $\textit{Escherichia coli}$
Untersuchungen zur Membranintegrität während der Tat-abhängigen Proteintranslokation in $\textit{Escherichia coli}$
The twin arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane of bacteria. The Tat-translocase is composed of the proteins TatA. TatB, TatC and TatE, but the ratio of these proteins and their interaction in the active Tat complex is not completely known up...
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Personal Name(s): | Fleckenstein, Stefan (Corresponding author) |
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Contributing Institute: |
Biotechnologie; IBG-1 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2012
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Physical Description: |
155 p. |
Dissertation Note: |
Heinrich-Heine-Universität Düsseldorf, Diss., 2012 |
ISBN: |
978-3-89336-841-9 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
ohne Topic |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Gesundheit / Health
60 |
Subject (ZB): | |
Publikationsportal JuSER |
The twin arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane of bacteria. The Tat-translocase is composed of the proteins TatA. TatB, TatC and TatE, but the ratio of these proteins and their interaction in the active Tat complex is not completely known up to date. Besides, it is not fully understood how the cell manages to maintain membrane integrity and to prevent passive influx, respectively efflux, of other molecules across the membrane during the translocation process of a folded substrate. Within this study the following results were obtained: (1) The Tat-translocase is evolutionarily perfectly adapted to native substrates and able to translocate them while maintaining membrane integrity. In contrast it is not adapted to artificial substrates. Hence, translocation of artificial substrates causes leakage, leading to an impairment of the membrane integrity. Hereby, in addition to the high energy requirements for the translocation process of Tat-substrates, the amount of protons entering the cytoplasm passively per translocated substrate is enhanced in relation to translocation of native substrates. Therefore total energy costs of the translocation process are increased. (2) Due to increased total energy costs the translocation of artificial substrates across the membrane is associated with a growth inhibition of the respective strain. The degree of translocation of artificial Tat substrates correlates with the degree of growth inhibition. (3) When – in addition to a high degree of translocation of the artificial Tat substrate TorAMalE – the conformation of the Tat-translocase is changed by a mutation in a way to promote even bigger leakage during translocation of TorA MalE as in the case of strain GSJ101 [Δtat pTM, pTatAB(L9P)C], then an even larger amount of protons can passively enter the cytoplasm per translocated substrate in relation to translocation by the wild-type Tattranslocase. Thus the total amount of energy required for the translocation process is further increased, leading to an even more pronounced growth inhibition. (4) The growth inhibition of strain GSJ101 [Δtat, pTM, pTatAB (L9P) C] can be suppressed by Tat-coupled mutations in TatA, TatB and TatC. (5) Most of these suppressor mutations lead to an inhibition of the Tat-translocase. Due to a lower level of translocation of the artificial substrate TorA-MalE both the energy costs of translocation and the passive influx of protons associated with translocation of TorA-MalE are reduced. Consequently the overall energy costs are reduced as well. Some mutations even result in complete Tat-inactivation. (6) Few suppressor mutations lead to an adaptation of the mutant Tat-translocase to the artificial substrate TorA-MalE, thereby preventing impairment of the integrity of the [...] |