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- 주제어 : Membrane Biogenesis (검색결과 4 건)
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Refined topology model of the STT3/Stt3 protein subunit of the oligosaccharyltransferase complex
Lara, Patricia,Ojemalm, Karin,Reithinger, Johannes,Holgado, Aurora,Maojun, You,Hammed, Abdessalem,Mattle, Daniel,Kim, Hyun,Nilsson, IngMarie American Society for Biochemistry and Molecular Bi 2017 The Journal of biological chemistry Vol.292 No.27
<P>The oligosaccharyltransferase complex, localized in the endoplasmic reticulum (ER) of eukaryotic cells, is responsible for the N-linked glycosylation of numerous protein substrates. The membrane protein STT3 is a highly conserved part of the oligosaccharyltransferase and likely contains the active site of the complex. However, understanding the catalytic determinants of this system has been challenging, in part because of a discrepancy in the structural topology of the bacterial versus eukaryotic proteins and incomplete information about the mechanism of membrane integration. Here, we use a glycosylation mapping approach to investigate these questions. We measured the membrane integration efficiency of the mouse STT3-A and yeast Stt3p transmembrane domains (TMDs) and report a refined topology of the N-terminal half of the mouse STT3-A. Our results show that most of the STT3 TMDs are well inserted into the ER membrane on their own or in the presence of the natural flanking residues. However, for the mouse STT3-A hydrophobic domains 4 and 6 and yeast Stt3p domains 2, 3a, 3c, and 6 we measured reduced insertion efficiency into the ER membrane. Furthermore, we mapped the first half of the STT3-A protein, finding two extra hydrophobic domains between the third and the fourthTMD. This result indicates that the eukaryotic STT3 has 13 transmembrane domains, consistent with the structure of the bacterial homolog of STT3 and setting the stage for future combined efforts to interrogate this fascinating system.</P>
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Bacterial Outer Membrane Vesicles as a Delivery System for Virulence Regulation
( Hyunjin Yoon ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.8
Outer membrane vesicles (OMVs) are spherical nanostructures that are ubiquitously shed from gram-negative bacteria both in vitro and in vivo. Recent findings revealed that OMVs, which contain diverse components derived from the parent bacterium, play an important role in communication with neighboring bacteria and the environment. Furthermore, nanoscale proteoliposomes decorated with pathogen-associated molecules attract considerable attention as a non-replicative carrier for vaccines and drug materials. This review introduces recent advances in OMV biogenesis and discusses the roles of OMVs in the context of bacterial communication and virulence regulation. It also describes the remarkable accomplishments in OMV engineering for diverse therapeutic applications.
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Gattis, Samuel G.,Chung, Hak Suk,Trent, M. Stephen,Raetz, Christian R. H. American Society for Biochemistry and Molecular Bi 2013 The Journal of biological chemistry Vol.288 No.13
<P>Lipopolysaccharide (LPS; endotoxin) is an essential component of the outer monolayer of nearly all Gram-negative bacteria. LPS is composed of a hydrophobic anchor, known as lipid A, an inner core oligosaccharide, and a repeating O-antigen polysaccharide. In nearly all species, the first sugar bridging the hydrophobic lipid A and the polysaccharide domain is 3-deoxy-<SMALL>d</SMALL>-manno-octulosonic acid (Kdo), and thus it is critically important for LPS biosynthesis. Modifications to lipid A have been shown to be important for resistance to antimicrobial peptides as well as modulating recognition by the mammalian innate immune system. Therefore, lipid A derivatives have been used for development of vaccine strains and vaccine adjuvants. One derivative that has yet to be studied is 8-amino-3,8-dideoxy-<SMALL>d</SMALL>-manno-octulosonic acid (Kdo8N), which is found exclusively in marine bacteria of the genus <I>Shewanella</I>. Using bioinformatics, a candidate gene cluster for Kdo8N biosynthesis was identified in <I>Shewanella oneidensis</I>. Expression of these genes recombinantly in <I>Escherichia coli</I> resulted in lipid A containing Kdo8N, and <I>in vitro</I> assays confirmed their proposed enzymatic function. Both the <I>in vivo</I> and <I>in vitro</I> data were consistent with direct conversion of Kdo to Kdo8N prior to its incorporation into the Kdo8N-lipid A domain of LPS by a metal-dependent oxidase followed by a glutamate-dependent aminotransferase. To our knowledge, this oxidase is the first enzyme shown to oxidize an alcohol using a metal and molecular oxygen, not NAD(P)<SUP>+</SUP>. Creation of an <I>S. oneidensis</I> in-frame deletion strain showed increased sensitivity to the cationic antimicrobial peptide polymyxin as well as bile salts, suggesting a role in outer membrane integrity.</P>
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Comparative Phenotypic Analysis of Anabaena sp. PCC 7120 Mutants of Porinlike Genes
( Hannah Schätzle ),( Eva-maria Brouwer ),( Elisa Liebhart ),( Mara Stevanovic ),( Enrico Schleiff ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.5
Porins are essential for the viability of Gram-negative bacteria. They ensure the uptake of nutrients, can be involved in the maintenance of outer membrane integrity and define the antibiotic or drug resistance of organisms. The function and structure of porins in proteobacteria is well described, while their function in photoautotrophic cyanobacteria has not been systematically explored. We compared the domain architecture of nine putative porins in the filamentous cyanobacterium Anabaena sp. PCC 7120 and analyzed the seven candidates with predicted OprB-domain. Single recombinant mutants of the seven genes were created and their growth capacity under different conditions was analyzed. Most of the putative porins seem to be involved in the transport of salt and copper, as respective mutants were resistant to elevated concentrations of these substances. In turn, only the mutant of alr2231 was less sensitive to elevated zinc concentrations, while mutants of alr0834, alr4741 and all4499 were resistant to high manganese concentrations. Notably the mutant of alr4550 shows a high sensitivity against harmful compounds, which is indicative for a function related to the maintenance of outer membrane integrity. Moreover, the mutant of all5191 exhibited a phenotype which suggests either a higher nitrate demand or an inefficient nitrogen fixation. The dependency of porin membrane insertion on Omp85 proteins was tested exemplarily for Alr4550, and an enhanced aggregation of Alr4550 was observed in two omp85 mutants. The comparative analysis of porin mutants suggests that the proteins in parts perform distinct functions related to envelope integrity and solute uptake.
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