The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Gail J Demmler - One of the best experts on this subject based on the ideXlab platform.
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comparison of the directigen flu a b Membrane Enzyme immunoassay with viral culture for rapid detection of influenza a and b viruses in respiratory specimens
Journal of Clinical Microbiology, 2004Co-Authors: Andreea C Cazacu, Sooyoung E Chung, Jewel Greer, Gail J DemmlerAbstract:The performance of a commercially available, rapid Membrane Enzyme immunoassay for influenza A and B virus detection was compared to that of viral culture in 4,092 respiratory specimens collected from patients presenting with respiratory symptoms during the 2002-2003 influenza season. The test's overall sensitivity was 43.83%, lower than previously reported but similar for detection of both influenza A and B viruses (42.98 versus 44.76%). However, specificity, 99.74%, was excellent for both influenza A and B viruses (99.82 versus 99.92%). These values make this test a very good confirmatory test when clinical suspicion is high, but a less accurate screening test for large populations.
Pei Zhou - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of mray an essential Membrane Enzyme for bacterial cell wall synthesis
Biophysical Journal, 2014Co-Authors: Ben C Chung, Jinshi Zhao, Robert A Gillespie, Doyeon Kwon, Ziqiang Guan, Jiyong Hong, Pei ZhouAbstract:The Phospho-MurNAc-pentapeptide translocase (MraY) is a prokaryotic Membrane-spanning Enzyme involved in an essential process of peptidoglycan synthesis: transfer the precursor phosphor-MurNAc-pentapeptide to carrier lipid undecaprenyl phosphate. MraY belongs to a subfamily of the polyprenyl-phosphate N-acetyl hexosamine 1-phosphate transferase (PNPT) superfamily whose members are involved in various biological processes including eukaryotic N-linked glycosylation. MraY has been a target for antibiotics development for its essentiality and specificity in bacteria. Therefore atomic structure of MraY can provides valuable mechanistic information that can aid development of new antibiotics. We report the crystal structure of MraY from Aquifex aeolicus (MraYAA), the first structure of the PNPT superfamily, at 3.3 A resolution. The crystal structure, together with crystallographic and functional studies, reveals the architecture of MraYAA, the location of Mg2+ at the active site and the putative binding sites of both substrates. Our crystallographic studies provide insights into the mechanism of how MraY attaches a building block of peptidoglycan to a carrier lipid.
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crystal structure of mray an essential Membrane Enzyme for bacterial cell wall synthesis
Science, 2013Co-Authors: Ben C Chung, Jinshi Zhao, Robert A Gillespie, Doyeon Kwon, Ziqiang Guan, Jiyong Hong, Pei ZhouAbstract:MraY (phospho-MurNAc-pentapeptide translocase) is an integral Membrane Enzyme that catalyzes an essential step of bacterial cell wall biosynthesis: the transfer of the peptidoglycan precursor phospho-MurNAc-pentapeptide to the lipid carrier undecaprenyl phosphate. MraY has long been considered a promising target for the development of antibiotics, but the lack of a structure has hindered mechanistic understanding of this critical Enzyme and the Enzyme superfamily in general. The superfamily includes Enzymes involved in bacterial lipopolysaccharide/teichoic acid formation and eukaryotic N-linked glycosylation, modifications that are central in many biological processes. We present the crystal structure of MraY from Aquifex aeolicus (MraYAA) at 3.3 A resolution, which allows us to visualize the overall architecture, locate Mg2+ within the active site, and provide a structural basis of catalysis for this class of Enzyme.
Russell E Bishop - One of the best experts on this subject based on the ideXlab platform.
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the integral Membrane Enzyme pagp alternates between two dynamically distinct states
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Peter M Hwang, Russell E BishopAbstract:PhoPQ-activated gene P (PagP) is an integral Membrane Enzyme that transfers the sn-1 palmitate chain from phospholipid to lipopolysaccharide in Gram-negative bacteria. A recent x-ray crystallographic study established that the sn-1 palmitate binds within a long cavity at the center of the PagP β barrel. The high mobility required to permit substrate entry into the central core of the barrel contrasts with the need to assemble a well defined structure in the peripheral loops, where many key catalytic residues are located. To gain insight into how dynamics relate to the function of PagP, the Enzyme was reconstituted into CYFOS-7, a detergent that supports enzymatic activity. Under these conditions, PagP exists in equilibrium between two states, relaxed (R) and tense (T). The kinetics and thermodynamics of the interchange have been investigated by 1H-15N NMR spectroscopy, with ΔH = -10.7 kcal/mol and ΔS = -37.5 cal/mol·K for the R→ T transition. A comparison of chemical shifts between the two states indicates that major structural changes occur in the large extracellular L1 loop and adjacent regions of the β barrel. In addition to the R,T interconversion, other conformational exchange processes are observed in the R state, showing it to be quite flexible. Thus a picture emerges in which substrate entry is facilitated by the mobility of the R state, whereas the relatively rigid T state adopts a radically different conformation in a region of the protein known to be essential for catalysis. The ability to switch between dynamically distinct states may be a key feature of the catalytic cycle of PagP.
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solution structure and dynamics of the outer Membrane Enzyme pagp by nmr
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Peter M Hwang, Wingyiu Choy, Eileen I Lo, Lu Chen, Julie D Formankay, Christian R H Raetz, Gilbert G Prive, Russell E BishopAbstract:The bacterial outer Membrane Enzyme PagP transfers a palmitate chain from a phospholipid to lipid A. In a number of pathogenic Gram-negative bacteria, PagP confers resistance to certain cationic antimicrobial peptides produced during the host innate immune response. The global fold of Escherichia coli PagP was determined in both dodecylphosphocholine and n-octyl-β-d-glucoside detergent micelles using solution NMR spectroscopy. PagP consists of an eight-stranded anti-parallel β-barrel preceded by an amphipathic α helix. The β-barrel is well defined, whereas NMR relaxation measurements reveal considerable mobility in the loops connecting individual β-strands. Three amino acid residues critical for enzymatic activity localize to extracellular loops near the Membrane interface, positioning them optimally to interact with the polar headgroups of lipid A. Hence, the active site of PagP is situated on the outer surface of the outer Membrane. Because the phospholipids that donate palmitate in the enzymatic reaction are normally found only in the inner leaflet of the outer Membrane, PagP activity may depend on the aberrant migration of phospholipids into the outer leaflet. This finding is consistent with an emerging paradigm for outer Membrane Enzymes in providing an adaptive response toward disturbances in the outer Membrane.
Ben C Chung - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of mray an essential Membrane Enzyme for bacterial cell wall synthesis
Biophysical Journal, 2014Co-Authors: Ben C Chung, Jinshi Zhao, Robert A Gillespie, Doyeon Kwon, Ziqiang Guan, Jiyong Hong, Pei ZhouAbstract:The Phospho-MurNAc-pentapeptide translocase (MraY) is a prokaryotic Membrane-spanning Enzyme involved in an essential process of peptidoglycan synthesis: transfer the precursor phosphor-MurNAc-pentapeptide to carrier lipid undecaprenyl phosphate. MraY belongs to a subfamily of the polyprenyl-phosphate N-acetyl hexosamine 1-phosphate transferase (PNPT) superfamily whose members are involved in various biological processes including eukaryotic N-linked glycosylation. MraY has been a target for antibiotics development for its essentiality and specificity in bacteria. Therefore atomic structure of MraY can provides valuable mechanistic information that can aid development of new antibiotics. We report the crystal structure of MraY from Aquifex aeolicus (MraYAA), the first structure of the PNPT superfamily, at 3.3 A resolution. The crystal structure, together with crystallographic and functional studies, reveals the architecture of MraYAA, the location of Mg2+ at the active site and the putative binding sites of both substrates. Our crystallographic studies provide insights into the mechanism of how MraY attaches a building block of peptidoglycan to a carrier lipid.
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crystal structure of mray an essential Membrane Enzyme for bacterial cell wall synthesis
Science, 2013Co-Authors: Ben C Chung, Jinshi Zhao, Robert A Gillespie, Doyeon Kwon, Ziqiang Guan, Jiyong Hong, Pei ZhouAbstract:MraY (phospho-MurNAc-pentapeptide translocase) is an integral Membrane Enzyme that catalyzes an essential step of bacterial cell wall biosynthesis: the transfer of the peptidoglycan precursor phospho-MurNAc-pentapeptide to the lipid carrier undecaprenyl phosphate. MraY has long been considered a promising target for the development of antibiotics, but the lack of a structure has hindered mechanistic understanding of this critical Enzyme and the Enzyme superfamily in general. The superfamily includes Enzymes involved in bacterial lipopolysaccharide/teichoic acid formation and eukaryotic N-linked glycosylation, modifications that are central in many biological processes. We present the crystal structure of MraY from Aquifex aeolicus (MraYAA) at 3.3 A resolution, which allows us to visualize the overall architecture, locate Mg2+ within the active site, and provide a structural basis of catalysis for this class of Enzyme.
Peter M Hwang - One of the best experts on this subject based on the ideXlab platform.
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Topology of an outer-Membrane Enzyme: Measuring oxygen and water contacts in solution NMR studies of PagP.
Journal of the American Chemical Society, 2006Co-Authors: Ferenc Evanics, Peter M Hwang, Yao Cheng, † Lewis E. Kay, R. Scott ProsserAbstract:The topology of the bacterial outer-Membrane Enzyme, PagP, in dodecylphosphocholine micelles was studied by solution NMR using oxygen and water contacts as probes of hydrophobicity and topology. The effects of oxygen on amide protons were measured at an oxygen partial pressure of 20 atm through the paramagnetic contribution to the relaxation rates associated with the decay of two-spin order. A significant gradation of paramagnetic rates was observed for backbone amides belonging to the transMembrane residues. These rates were observed to depend on immersion depth, local hydrophobicity, and steric effects. Variations in the paramagnetic relaxation rates due to local hydrophobicity or steric effects could be, to some extent, averaged out by considering an azimuthally averaged quantity. This averaged paramagnetic rate was found to have a distinct maximum exactly in the middle of the transMembrane domain of PagP, assuming the immersion depth axis is tilted by 25° with respect to the barrel axis. Contact betwe...
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the integral Membrane Enzyme pagp alternates between two dynamically distinct states
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Peter M Hwang, Russell E BishopAbstract:PhoPQ-activated gene P (PagP) is an integral Membrane Enzyme that transfers the sn-1 palmitate chain from phospholipid to lipopolysaccharide in Gram-negative bacteria. A recent x-ray crystallographic study established that the sn-1 palmitate binds within a long cavity at the center of the PagP β barrel. The high mobility required to permit substrate entry into the central core of the barrel contrasts with the need to assemble a well defined structure in the peripheral loops, where many key catalytic residues are located. To gain insight into how dynamics relate to the function of PagP, the Enzyme was reconstituted into CYFOS-7, a detergent that supports enzymatic activity. Under these conditions, PagP exists in equilibrium between two states, relaxed (R) and tense (T). The kinetics and thermodynamics of the interchange have been investigated by 1H-15N NMR spectroscopy, with ΔH = -10.7 kcal/mol and ΔS = -37.5 cal/mol·K for the R→ T transition. A comparison of chemical shifts between the two states indicates that major structural changes occur in the large extracellular L1 loop and adjacent regions of the β barrel. In addition to the R,T interconversion, other conformational exchange processes are observed in the R state, showing it to be quite flexible. Thus a picture emerges in which substrate entry is facilitated by the mobility of the R state, whereas the relatively rigid T state adopts a radically different conformation in a region of the protein known to be essential for catalysis. The ability to switch between dynamically distinct states may be a key feature of the catalytic cycle of PagP.
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solution structure and dynamics of the outer Membrane Enzyme pagp by nmr
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Peter M Hwang, Wingyiu Choy, Eileen I Lo, Lu Chen, Julie D Formankay, Christian R H Raetz, Gilbert G Prive, Russell E BishopAbstract:The bacterial outer Membrane Enzyme PagP transfers a palmitate chain from a phospholipid to lipid A. In a number of pathogenic Gram-negative bacteria, PagP confers resistance to certain cationic antimicrobial peptides produced during the host innate immune response. The global fold of Escherichia coli PagP was determined in both dodecylphosphocholine and n-octyl-β-d-glucoside detergent micelles using solution NMR spectroscopy. PagP consists of an eight-stranded anti-parallel β-barrel preceded by an amphipathic α helix. The β-barrel is well defined, whereas NMR relaxation measurements reveal considerable mobility in the loops connecting individual β-strands. Three amino acid residues critical for enzymatic activity localize to extracellular loops near the Membrane interface, positioning them optimally to interact with the polar headgroups of lipid A. Hence, the active site of PagP is situated on the outer surface of the outer Membrane. Because the phospholipids that donate palmitate in the enzymatic reaction are normally found only in the inner leaflet of the outer Membrane, PagP activity may depend on the aberrant migration of phospholipids into the outer leaflet. This finding is consistent with an emerging paradigm for outer Membrane Enzymes in providing an adaptive response toward disturbances in the outer Membrane.