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- Bamyaci, Sarp, et al.
(författare)
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YopN Is Required for Efficient Effector Translocation and Virulence in Yersinia pseudotuberculosis
- 2018
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Ingår i: Infection and Immunity. - : AMER SOC MICROBIOLOGY. - 0019-9567 .- 1098-5522. ; 86:8
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Tidskriftsartikel (refereegranskat)abstract
- Type III secretion systems (T3SSs) are used by various Gram-negative pathogens to subvert the host defense by a host cell contact-dependent mechanism to secrete and translocate virulence effectors. While the effectors differ between pathogens and determine the pathogenic life style, the overall mechanism of secretion and translocation is conserved. T3SSs are regulated at multiple levels, and some secreted substrates have also been shown to function in regulation. In Yersinia, one of the substrates, YopN, has long been known to function in the host cell contact-dependent regulation of the T3SS. Prior to contact, through its interaction with TyeA, YopN blocks secretion. Upon cell contact, TyeA dissociates from YopN, which is secreted by the T3SS, resulting in the induction of the system. YopN has also been shown to be translocated into target cells by a T3SS-dependent mechanism. However, no intracellular function has yet been assigned to YopN. The regulatory role of YopN involves the N-terminal and C-terminal parts, while less is known about the role of the central region of YopN. Here, we constructed different in-frame deletion mutants within the central region. The deletion of amino acids 76 to 181 resulted in an unaltered regulation of Yop expression and secretion but triggered reduced YopE and YopH translocation within the first 30 min after infection. As a consequence, this deletion mutant lost its ability to block phagocytosis by macrophages. In conclusion, we were able to differentiate the function of YopN in translocation and virulence from its function in regulation.
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| 2. |
- Costa, Tiago, et al.
(författare)
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Measurement of Yersinia translocon pore formation in erythrocytes
- 2019
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Ingår i: Pathogenic Yersinia. - New York, NY, U.S.A. : Humana Press. - 9781493995400 ; , s. 211-229
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Bokkapitel (refereegranskat)abstract
- Many Gram-negative pathogens produce a type III secretion system capable of intoxicating eukaryotic cells with immune-modulating effector proteins. Fundamental to this injection process is the prior secretion of two translocator proteins destined for injectisome translocon pore assembly within the host cell plasma membrane. It is through this pore that effectors are believed to travel to gain access to the host cell interior. Yersinia species especially pathogenic to humans and animals assemble this translocon pore utilizing two hydrophobic translocator proteins-YopB and YopD. Although a full molecular understanding of the biogenesis, function and regulation of this translocon pore and subsequent effector delivery into host cells remains elusive, some of what we know about these processes can be attributed to studies of bacterial infections of erythrocytes. Herein we describe the methodology of erythrocyte infections by Yersinia, and how analysis of the resultant contact-dependent hemolysis can serve as a relative measurement of YopB- and YopD-dependent translocon pore formation.
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| 3. |
- Edgren, Tomas, 1971-
(författare)
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Electron transport to nitrogenase in Rhodospirillum rubrum
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological nitrogen fixation is a key step in the global nitrogen cycle. In this process, dinitrogen in the air is converted to biologically accessible ammonia, which is further assimilated in to the biosphere. Nitrogenase, the enzyme system responsible for dinitrogen reduction, is only found in prokaryotic organisms and biological nitrogen fixation is an energy-demanding process, requiring both ATP and low potential reducing equivalents. In the free-living purple non-sulfur anoxygenic phototroph Rhodospirillum rubrum, efficient electron transfer to nitrogenase is dependent on active electron transport in the chromatophore membrane.I have shown that reducing equivalents for nitrogen fixation is generated through the action of the proteins encoded by the fixABCX genes. The membrane associated protein complex encoded by these genes reduces a soluble ferredoxin, which in turn acts as the direct electron donor to nitrogenase in this organism. The heterodimeric flavoprotein FixAB has NADH dehydrogenase activity indicating that the reducing equivalents for nitrogen fixation are derived from the general metabolism of the cell. The membrane associated FixC protein is believed to drive the energetically unfavorable reduction of ferredoxin N using energy derived from the electron transfer processes in the chromatophore membrane in some unknown manner. The membrane associated protein complex encoded by fixABCX most likely constitutes the unknown link between photosynthesis and nitrogen fixation in R. rubrum.
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