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Pankaj Deo, Seong H Chow, Iain D Hay, Oded Kleifeld, Adam Costin, Kirstin D Elgass, Jhih-Hang Jiang, Georg Ramm, Kipros Gabriel, Gordon Dougan, Trevor Lithgow, Eva Heinz, Thomas Naderer
Neisseria gonorrhoeae causes the sexually transmitted disease gonorrhoea by evading innate immunity. Colonizing the mucosa of the reproductive tract depends on the bacterial outer membrane porin, PorB, which is essential for ion and nutrient uptake. PorB is also targeted to host mitochondria and regulates apoptosis pathways to promote infections. How PorB traffics from the outer membrane of N. gonorrhoeae to mitochondria and whether it modulates innate immune cells, such as macrophages, remains unclear. Here, we show that N...
March 2018: PLoS Pathogens
Phillip Nagley, Justin St John, Kipros Gabriel, Matthew McKenzie
No abstract text is available yet for this article.
April 2014: Biochimica et Biophysica Acta
Victoria L Hewitt, Kipros Gabriel, Ana Traven
BACKGROUND: Mitochondrial biogenesis is an essential process in all eukaryotes. Import of proteins from the cytosol into mitochondria is a key step in organelle biogenesis. Recent evidence suggests that a given mitochondrial protein does not take the same import route in all organisms, suggesting that pathways of mitochondrial protein import can be rewired through evolution. Examples of this process so far involve proteins destined to the mitochondrial intermembrane space (IMS). SCOPE OF REVIEW: Here we review the components, substrates and energy sources of the known mechanisms of protein import into the IMS...
April 2014: Biochimica et Biophysica Acta
Victoria L Hewitt, Eva Heinz, Miguel Shingu-Vazquez, Yue Qu, Branka Jelicic, Tricia L Lo, Traude H Beilharz, Geoff Dumsday, Kipros Gabriel, Ana Traven, Trevor Lithgow
The controlled biogenesis of mitochondria is a key cellular system coordinated with the cell division cycle, and major efforts in systems biology currently are directed toward understanding of the control points at which this coordination is achieved. Here we present insights into the function, evolution, and regulation of mitochondrial biogenesis through the study of the protein import machinery in the human fungal pathogen, Candida albicans. Features that distinguish C. albicans from baker's yeast (Saccharomyces cerevisiae) include the stringency of metabolic control at the level of oxygen consumption, the potential for ATP exchange through the porin in the outer membrane, and components and domains in the sorting and assembling machinery complex, a molecular machine that drives the assembly of proteins in the outer mitochondrial membrane...
December 4, 2012: Proceedings of the National Academy of Sciences of the United States of America
Jhih-Hang Jiang, Janette Tong, Kher Shing Tan, Kipros Gabriel
β-barrel proteins are the highly abundant in the outer membranes of Gram-negative bacteria and the mitochondria in eukaryotes. The assembly of β-barrels is mediated by two evolutionary conserved machineries; the β-barrel Assembly Machinery (BAM) in Gram-negative bacteria; and the Sorting and Assembly Machinery (SAM) in mitochondria. Although the BAM and SAM have functionally conserved roles in the membrane integration and folding of β-barrel proteins, apart from the central BamA and Sam50 proteins, the remaining components of each of the complexes have diverged remarkably...
2012: International Journal of Molecular Sciences
Samuel L Palframan, Terry Kwok, Kipros Gabriel
More than 50% of the world's population is infected with Helicobacter pylori (H. pylori). Chronic infection with this Gram-negative pathogen is associated with the development of peptic ulcers and is linked to an increased risk of gastric cancer. H. pylori secretes many proteinaceous factors that are important for initial colonization and subsequent persistence in the host stomach. One of the major protein toxins secreted by H. pylori is the Vacuolating cytotoxin A (VacA). After secretion from the bacteria via a type V autotransport secretion system, the 88 kDa VacA toxin (comprised of the p33 and p55 subunits) binds to host cells and is internalized, causing severe "vacuolation" characterized by the accumulation of large vesicles that possess hallmarks of both late endosomes and early lysosomes...
2012: Frontiers in Cellular and Infection Microbiology
Chou Hung Sim, Kipros Gabriel, Ryan D Mills, Janetta G Culvenor, Heung-Chin Cheng
Mutations of the phosphatase and tensin homolog (PTEN)-induced kinase 1 (PINK1) gene can cause early-onset familial Parkinson disease (PD). PINK1 encodes a neuroprotective protein kinase localized at the mitochondria, and its involvement in regulating mitochondrial dynamics, trafficking, structure, and function is well documented. Owing to the lack of information on structure and biochemical properties for PINK1, exactly how PINK1 exerts its neuroprotective function and how the PD-causative mutations impact on PINK1 structure and function remain unclear...
October 2012: Human Mutation
Jhih-Hang Jiang, Janette Tong, Kipros Gabriel
Bacterial infection has enormous global social and economic impacts stemming from effects on human health and agriculture. Although there are still many unanswered questions, decades of research has uncovered many of the pathogenic mechanisms at play. It is now clear that bacterial pathogens produce a plethora of proteins known as "toxins" and "effectors" that target a variety of physiological host processes during the course of infection. One of the targets of host targeted bacterial toxins and effectors are the mitochondria...
May 2012: IUBMB Life
Pavel Dolezal, Margareta Aili, Janette Tong, Jhih-Hang Jiang, Carlo M T Marobbio, Carlo M Marobbio, Sau Fung Lee, Ralf Schuelein, Simon Belluzzo, Eva Binova, Aurelie Mousnier, Gad Frankel, Giulia Giannuzzi, Ferdinando Palmieri, Kipros Gabriel, Thomas Naderer, Elizabeth L Hartland, Trevor Lithgow
The Mitochondrial Carrier Family (MCF) is a signature group of integral membrane proteins that transport metabolites across the mitochondrial inner membrane in eukaryotes. MCF proteins are characterized by six transmembrane segments that assemble to form a highly-selective channel for metabolite transport. We discovered a novel MCF member, termed Legionellanucleotide carrier Protein (LncP), encoded in the genome of Legionella pneumophila, the causative agent of Legionnaire's disease. LncP was secreted via the bacterial Dot/Icm type IV secretion system into macrophages and assembled in the mitochondrial inner membrane...
January 2012: PLoS Pathogens
Jhih-Hang Jiang, John K Davies, Trevor Lithgow, Richard A Strugnell, Kipros Gabriel
Mitochondria originated from Gram-negative bacteria through endosymbiosis. In modern day mitochondria, the Sorting and Assembly Machinery (SAM) is responsible for eukaryotic β-barrel protein assembly in the mitochondrial outer membrane. The SAM is the functional equivalent of the β-barrel assembly machinery found in the outer membrane of Gram-negative bacteria. In this study we examined the import pathway of a pathogenic bacterial protein, PorB, which is targeted from pathogenic Neisseria to the host mitochondria...
November 2011: Molecular Microbiology
Janette Tong, Pavel Dolezal, Joel Selkrig, Simon Crawford, Alastair G B Simpson, Nicholas Noinaj, Susan K Buchanan, Kipros Gabriel, Trevor Lithgow
The evolution of mitochondria from ancestral bacteria required that new protein transport machinery be established. Recent controversy over the evolution of these new molecular machines hinges on the degree to which ancestral bacterial transporters contributed during the establishment of the new protein import pathway. Reclinomonas americana is a unicellular eukaryote with the most gene-rich mitochondrial genome known, and the large collection of membrane proteins encoded on the mitochondrial genome of R. americana includes a bacterial-type SecY protein transporter...
May 2011: Molecular Biology and Evolution
Jung Hock Foo, Janetta G Culvenor, Richard L Ferrero, Terry Kwok, Trevor Lithgow, Kipros Gabriel
Helicobacter pylori infection causes peptic ulcers and gastric cancer. A major toxin secreted by H. pylori is the bipartite vacuolating cytotoxin A, VacA. The toxin is believed to enter host cells as two subunits: the p55 subunit (55 kDa) and the p33 subunit (33 kDa). At the biochemical level, it has been shown that VacA forms through the assembly of large multimeric pores composed of both the p33 subunit and the p55 subunit in biological membranes. One of the major target organelles of VacA is the mitochondria...
September 3, 2010: Journal of Molecular Biology
Khatira Anwari, Sebastian Poggio, Andrew Perry, Xenia Gatsos, Sri Harsha Ramarathinam, Nicholas A Williamson, Nicholas Noinaj, Susan Buchanan, Kipros Gabriel, Anthony W Purcell, Christine Jacobs-Wagner, Trevor Lithgow
Mitochondria are organelles derived from an intracellular alpha-proteobacterium. The biogenesis of mitochondria relies on the assembly of beta-barrel proteins into the mitochondrial outer membrane, a process inherited from the bacterial ancestor. Caulobacter crescentus is an alpha-proteobacterium, and the BAM (beta-barrel assembly machinery) complex was purified and characterized from this model organism. Like the mitochondrial sorting and assembly machinery complex, we find the BAM complex to be modular in nature...
January 8, 2010: PloS One
Nicholas A Veldhuis, Ann P Gaeth, Richard B Pearson, Kipros Gabriel, James Camakaris
The copper-translocating Menkes (ATP7A, MNK protein) and Wilson (ATP7B, WND protein) P-type ATPases are pivotal for copper (Cu) homeostasis, functioning in the biosynthetic incorporation of Cu into copper-dependent enzymes of the secretory pathway, Cu detoxification via Cu efflux, and specialized roles such as systemic Cu absorption (MNK) and Cu excretion (WND). Essential to these functions is their Cu and hormone-responsive distribution between the trans-Golgi network (TGN) and exocytic vesicles located at or proximal to the apical (WND) or basolateral (MNK) cell surface...
February 2009: Biometals: An International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine
Diana Stojanovski, Dusanka Milenkovic, Judith M Müller, Kipros Gabriel, Agnes Schulze-Specking, Michael J Baker, Michael T Ryan, Bernard Guiard, Nikolaus Pfanner, Agnieszka Chacinska
The biogenesis of mitochondrial intermembrane space proteins depends on specific machinery that transfers disulfide bonds to precursor proteins. The machinery shares features with protein relays for disulfide bond formation in the bacterial periplasm and endoplasmic reticulum. A disulfide-generating enzyme/sulfhydryl oxidase oxidizes a disulfide carrier protein, which in turn transfers a disulfide to the substrate protein. Current views suggest that the disulfide carrier alternates between binding to the oxidase and the substrate...
October 20, 2008: Journal of Cell Biology
Agnieszka Chacinska, Bernard Guiard, Judith M Müller, Agnes Schulze-Specking, Kipros Gabriel, Stephan Kutik, Nikolaus Pfanner
Mitochondrial precursor proteins are directed into the intermembrane space via two different routes, the presequence pathway and the redox-dependent MIA pathway. The pathways were assumed to be independent and transport different proteins. We report that the intermembrane space receptor Mia40 can switch between both pathways. In fungi, Mia40 is synthesized as large protein with an N-terminal presequence, whereas in metazoans and plants, Mia40 consists only of the conserved C-terminal domain. Human MIA40 and the C-terminal domain of yeast Mia40 (termed Mia40(core)) rescued the viability of Mia40-deficient yeast independently of the presence of a presequence...
October 31, 2008: Journal of Biological Chemistry
Kipros Gabriel, Nikolaus Pfanner
Mitochondria contain a small genome that codes for approx 1% of the total number of proteins that reside in the mitochondria. Hence, most mitochondrial proteins are encoded for by the nuclear genome. After transcription in the nucleus these proteins are synthesized by cytosolic ribosomes. Like proteins destined for other organellar compartments, mitochondrially destined proteins possess targeting signals within their primary or secondary structure that direct them to the organelle with the assistance of cytosolic factors...
2007: Methods in Molecular Biology
Maria Concetta Renda, George Makrydimas, Kipros H Nicolaides, Emanuela Fecarotta, Gianfranca Damiani, Francesco Picciotto, Maria Cristina Jakil, Aurelio Maggio
Coelocentesis offers a new opportunity for gaining access to the human embryos from 28 d postfertilization. However, while some studies about its biochemical composition have been reported, our knowledge about immunological pattern of this compartment is still limited. For this reason, we studied the human coelomic fluids sampled from 6.6 to 10 wk of gestation. The majority of cellular population consisted in mesenchymal/epithelial cells. In fluids sampled before 10 wk we found only a preT Cell Receptor expression and an absence or a very low frequency of B lymphocytes, T lymphocytes and NK (natural killer) antigens...
November 2007: European Journal of Haematology
Dusanka Milenkovic, Kipros Gabriel, Bernard Guiard, Agnes Schulze-Specking, Nikolaus Pfanner, Agnieszka Chacinska
The mitochondrial intermembrane space (IMS) contains an essential machinery for protein import and assembly (MIA). Biogenesis of IMS proteins involves a disulfide relay between precursor proteins, the cysteine-rich IMS protein Mia40 and the sulfhydryl oxidase Erv1. How precursor proteins are specifically directed to the IMS has remained unknown. Here we systematically analyzed the role of cysteine residues in the biogenesis of the essential IMS chaperone complex Tim9-Tim10. Although each of the four cysteines of Tim9, as well as of Tim10, is required for assembly of the chaperone complex, only the most amino-terminal cysteine residue of each precursor is critical for translocation across the outer membrane and interaction with Mia40...
August 3, 2007: Journal of Biological Chemistry
Kipros Gabriel, Dusanka Milenkovic, Agnieszka Chacinska, Judith Müller, Bernard Guiard, Nikolaus Pfanner, Chris Meisinger
Mitochondria consist of four compartments, the outer membrane, intermembrane space (IMS), inner membrane and the matrix. Most mitochondrial proteins are synthesized as precursors in the cytosol and have to be imported into these compartments. While the protein import machineries of the outer membrane, inner membrane and matrix have been investigated in detail, a specific mitochondrial machinery for import and assembly of IMS proteins, termed MIA, was identified only recently. To date, only a very small number of substrate proteins of the MIA pathway have been identified...
January 19, 2007: Journal of Molecular Biology
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