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Shi Y Ghosh M Kovtunovych G Crooks DR Rouault TA 《Biochimica et biophysica acta》2012,1823(2):484-492
Ferredoxins are iron-sulfur proteins that have been studied for decades because of their role in facilitating the monooxygenase reactions catalyzed by p450 enzymes. More recently, studies in bacteria and yeast have demonstrated important roles for ferredoxin and ferredoxin reductase in iron-sulfur cluster assembly. The human genome contains two homologous ferredoxins, ferredoxin 1 (FDX1) and ferredoxin 2 (FDX2--formerly known as ferredoxin 1L). More recently, the roles of these two human ferredoxins in iron-sulfur cluster assembly were assessed, and it was concluded that FDX1 was important solely for its interaction with p450 enzymes to synthesize mitochondrial steroid precursors, whereas FDX2 was used for synthesis of iron-sulfur clusters, but not steroidogenesis. To further assess the role of the FDX-FDXR system in mammalian iron-sulfur cluster biogenesis, we performed siRNA studies on FDX1 and FDX2, on several human cell lines, using oligonucleotides identical to those previously used, along with new oligonucleotides that specifically targeted each gene. We concluded that both FDX1 and FDX2 were important in iron-sulfur cluster biogenesis. Loss of FDX1 activity disrupted activity of iron-sulfur cluster enzymes and cellular iron homeostasis, causing mitochondrial iron overload and cytosolic iron depletion. Moreover, knockdown of the sole human ferredoxin reductase, FDXR, diminished iron-sulfur cluster assembly and caused mitochondrial iron overload in conjunction with cytosolic depletion. Our studies suggest that interference with any of the three related genes, FDX1, FDX2 or FDXR, disrupts iron-sulfur cluster assembly and maintenance of normal cytosolic and mitochondrial iron homeostasis. 相似文献
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Belov GA Altan-Bonnet N Kovtunovych G Jackson CL Lippincott-Schwartz J Ehrenfeld E 《Journal of virology》2007,81(2):558-567
Infection of cells with poliovirus induces a massive intracellular membrane reorganization to form vesicle-like structures where viral RNA replication occurs. The mechanism of membrane remodeling remains unknown, although some observations have implicated components of the cellular secretory and/or autophagy pathways. Recently, we showed that some members of the Arf family of small GTPases, which control secretory trafficking, became membrane-bound after the synthesis of poliovirus proteins in vitro and associated with newly formed membranous RNA replication complexes in infected cells. The recruitment of Arfs to specific target membranes is mediated by a group of guanine nucleotide exchange factors (GEFs) that recycle Arf from its inactive, GDP-bound state to an active GTP-bound form. Here we show that two different viral proteins independently recruit different Arf GEFs (GBF1 and BIG1/2) to the new structures that support virus replication. Intracellular Arf-GTP levels increase approximately 4-fold during poliovirus infection. The requirement for these GEFs explains the sensitivity of virus growth to brefeldin A, which can be rescued by the overexpression of GBF1. The recruitment of Arf to membranes via specific GEFs by poliovirus proteins provides an important clue toward identifying cellular pathways utilized by the virus to form its membranous replication complex. 相似文献
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Manik C. Ghosh De-Liang Zhang Suh Young Jeong Gennadiy Kovtunovych Hayden Ollivierre-Wilson Audrey Noguchi Tiffany Tu Thomas Senecal Gabrielle Robinson Daniel R. Crooks Wing-Hang Tong Kavitha Ramaswamy Anamika Singh Brian B. Graham Rubin M. Tuder Zu-Xi Yu Michael Eckhaus Jaekwon Lee Tracey A. Rouault 《Cell metabolism》2013,17(2):271-281
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George A. Belov Gennadiy Kovtunovych Catherine L. Jackson Ellie Ehrenfeld 《Cellular microbiology》2010,12(10):1463-1479
Viruses are intracellular parasites whose reproduction relies on factors provided by the host. The cellular protein GBF1 is critical for poliovirus replication. Here we show that the contribution of GBF1 to virus replication is different from its known activities in uninfected cells. Normally GBF1 activates the ADP‐ribosylation factor (Arf) GTPases necessary for formation of COPI transport vesicles. GBF1 function is modulated by p115 and Rab1b. However, in polio‐infected cells, p115 is degraded and neither p115 nor Rab1b knock‐down affects virus replication. Poliovirus infection is very sensitive to brefeldin A (BFA), an inhibitor of Arf activation by GBF1. BFA targets the catalytic Sec7 domain of GBF1. Nevertheless the BFA block of polio replication is rescued by expression of only the N‐terminal region of GBF1 lacking the Sec7 domain. Replication of BFA‐resistant poliovirus in the presence of BFA is uncoupled from Arf activation but is dependent on GBF1. Thus the function(s) of this protein essential for viral replication can be separated from those required for cellular metabolism. 相似文献
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Correlation between pectate lyase activity and ability of diazotrophic Klebsiella oxytoca VN 13 to penetrate into plant tissues 总被引:2,自引:0,他引:2
Kovtunovych G. Lar O. Kamalova S. Kordyum V. Kleiner D. Kozyrovska N. 《Plant and Soil》1999,215(1):1-6
Diazotrophic Klebsiella oxytoca VN 13 was able to lyse pectate, but the lytic activity of cultures grown on non-selective
media was weak, and the enzyme was located mainly inside the cells. A small fraction of the population (10-6 to 10-5) was able to grow in a selective medium with sodium polygalacturonate as sole carbon source, and produced increased amounts
of the pectinolytic enzyme pectate lyase. When wheat seeds were inoculated with these bacteria, increased levels of this enzyme
correlated with a higher rate of internal colonization of wheat roots and with stimulation of wheat growth resulting in higher
biomass. This suggests that colonization occurs via lyzed pectin layers.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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