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Hua Xiang - One of the best experts on this subject based on the ideXlab platform.
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Association between the dynamics of multiple replication origins and the evolution of multireplicon genome architecture in haloarchaea
Genome Biology and Evolution, 2014Co-Authors: Zhenfang Wu, Haibo Yang, Lei Wang, Hua XiangAbstract:Haloarchaeal genomes are generally composed of multiple replicons, and each replicon has a single or multiple replication origin(s). The comparative genomic analysis of replication origins from closely related species can be used to reveal the evolutionary mechanisms that account for the development of multiple origin systems. Multiple replication origins have been in silico and experimentally investigated in Haloarcula hispanica, which raise the possibility for comparisons of multiple replication origins in Haloarcula species. Thus, we performed a comparison of H. hispanica replication origins with those from five additional Haloarcula species. We demonstrated that the multiple replication origins in the chromosome were evolved independently multiple times from the oriC1-dependent ancestral chromosome. Particularly, the two origins oriC1 and oriC2 were conserved in location, and both of them were adjacent to an rRNA operon, suggestive of correlations in replication and expression of surrounding genes that may promote the conservation of these two origins. Some chromosomal variable regions were used as hotspots for origin evolution in which replication origins were continually being acquired, lost, and disrupted. Furthermore, we demonstrated that autonomously replicating sequence plasmids with H. hispanica minichromosomal replication origins were extremely unstable. Because both organization and replication origins of minichromosomes were not conserved, we proposed an association between the evolution of extrachromosomal replicons and origin variation. Taken together, we provided insights into the evolutionary history of multiple replication origins in Haloarcula species, and proposed a general model of association between the dynamics of multiple replication origins and the evolution of multireplicon genome architecture in haloarchaea.
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Xiang H: Identification of the polyhydroxyalkanoate (PHA)-specific acetoacetyl-CoA reductase from multiple FabG paralogs in Haloarcula hispanica and reconstruction of PHA biosynthetic pathway in Haloferax volcanii
2013Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (�-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the �fabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea. Several haloarchaeal species belonging to the genera Haloferax, Haloarcula, Natrialba, and Haloquadratum are capable of synthesizing short-chain-length polyhydroxyalkanoates (SCL-PHAs) (6, 8, 14, 16), a large family of biopolymers with desirable biodegradability, biocompatibility, and thermoplastic features (31). Although the metabolic pathways of PHAs in bacteri
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Diversity and evolution of multiple orc/cdc6-adjacent replication origins in haloarchaea
BMC Genomics, 2012Co-Authors: Zhenfang Wu, Jingfang Liu, Hailong Liu, Xiaoqing Liu, Hua XiangAbstract:BackgroundWhile multiple replication origins have been observed in archaea, considerably less is known about their evolutionary processes. Here, we performed a comparative analysis of the predicted (proved in part) orc/cdc6 -associated replication origins in 15 completely sequenced haloarchaeal genomes to investigate the diversity and evolution of replication origins in halophilic Archaea.ResultsMultiple orc/cdc6 -associated replication origins were predicted in all of the analyzed haloarchaeal genomes following the identification of putative ORBs (origin recognition boxes) that are associated with orc/cdc6 genes. Five of these predicted replication origins in Haloarcula hispanica were experimentally confirmed via autonomous replication activities. Strikingly, several predicted replication origins in H. hispanica and Haloarcula marismortui are located in the distinct regions of their highly homologous chromosomes, suggesting that these replication origins might have been introduced as parts of new genomic content. A comparison of the origin-associated Orc/Cdc6 homologs and the corresponding predicted ORB elements revealed that the replication origins in a given haloarchaeon are quite diverse, while different haloarchaea can share a few conserved origins. Phylogenetic and genomic context analyses suggested that there is an original replication origin ( oriC1 ) that was inherited from the ancestor of archaea, and several other origins were likely evolved and/or translocated within the haloarchaeal species.ConclusionThis study provides detailed information about the diversity of multiple orc/cdc6 -associated replication origins in haloarchaeal genomes, and provides novel insight into the evolution of multiple replication origins in Archaea.
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Identification of the Polyhydroxyalkanoate (PHA)-Specific Acetoacetyl Coenzyme A Reductase among Multiple FabG Paralogs in Haloarcula hispanica and Reconstruction of the PHA Biosynthetic Pathway in Haloferax volcanii
Applied and environmental microbiology, 2009Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (beta-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the DeltafabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea.
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molecular characterization of the phaechm genes required for biosynthesis of poly 3 hydroxybutyrate in the extremely halophilic archaeon Haloarcula marismortui
Applied and Environmental Microbiology, 2007Co-Authors: Jing Han, Jian Zhou, Ligang Zhou, Hua XiangAbstract:Received 28 April 2007/Accepted 28 July 2007 Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of Archaea have not yet been experimentally investigated yet. In this study, we revealed that Haloarcula marismortui was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the phaEHm and phaCHm genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaCHm was revealed to be strongly bound with the PHB granules, but PhaEHm seemed not to be. Introduction of either the phaEHm or phaCHm gene into Haloarcula hispanica, which harbors highly homologous phaECHh genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the phaECHh genes in H. hispanica led to a complete loss of the PHA synthase activity. Complementation with phaECHm genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this phaEC-deleted haloarchaeon. These results indicated that the phaEC genes are required for biosynthesis of PHB and might encode an active PHA synthase in the Haloarcula species. Polyhydroxyalkanoates (PHAs) are a class of biodegradable polyesters of (R)-hydroxyalkanoates. These water-insoluble biopolymers are accumulated by a wide variety of bacteria and haloarchaea when the carbon source is available in excess but other nutrients are growth limiting (29). PHAs are attracting increasing attention due to their biodegradable, biocompatible, and thermoplastic features; thus, they are potential substitutes for petrochemical-derived plastics and can be used as packaging and biomedical materials, nonwoven fabrics, and flavor delivery agents (26). Nevertheless, the expensive cost for
Peter B. Moore - One of the best experts on this subject based on the ideXlab platform.
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Inhibitors of the Large Ribosomal Subunit from Haloarcula marismortui
Israel Journal of Chemistry, 2010Co-Authors: Peter B. MooreAbstract:The crystal structures that have been obtained for 23 different inhibitors bound to the large ribosomal subunit from Haloarcula marismortui are reviewed here. These structures provide important insights into how anti-ribosomal antibiotics inhibit protein synthesis, how species specificity arises, and the relationship between ribosomal mutations and antibiotic resistance. These structural studies also provide compelling evidence that the conformation of the peptidyl transferase center of the large ribosomal subunit is intrinsically variable, and that conformational equilibria play a role in determining its functional properties.
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Structures of Triacetyloleandomycin and Mycalamide A Bind to the Large Ribosomal Subunit of Haloarcula marismortui
Antimicrobial Agents and Chemotherapy, 2009Co-Authors: G. Gurel, Thomas A Steitz, Gregor Blaha, Peter B. MooreAbstract:Structures have been obtained for the complexes that triacetyloleandomycin and mycalamide A form with the large ribosomal subunit of Haloarcula marismortui. Triacetyloleandomycin binds in the nascent peptide tunnel and inhibits the activity of ribosomes by blocking the growth of the nascent peptide chain. Mycalamide A binds to the E site and inhibits protein synthesis by occupying the space normally occupied by the CCA end of E-site-bound tRNAs.
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crystal structure of the oxazolidinone antibiotic linezolid bound to the 50s ribosomal subunit
Journal of Medicinal Chemistry, 2008Co-Authors: Joseph A Ippolito, Peter B. Moore, Thomas A Steitz, Francois Franceschi, Zoltan F Kanyo, Deping Wang, Erin M DuffyAbstract:The oxazolidinone antibacterials target the 50S subunit of prokaryotic ribosomes. To gain insight into their mechanism of action, the crystal structure of the canonical oxazolidinone, linezolid, has been determined bound to the Haloarcula marismortui 50S subunit. Linezolid binds the 50S A-site, near the catalytic center, which suggests that inhibition involves competition with incoming A-site substrates. These results provide a structural basis for the discovery of improved oxazolidinones active against emerging drug-resistant clinical strains.
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negamycin binds to the wall of the nascent chain exit tunnel of the 50s ribosomal subunit
Antimicrobial Agents and Chemotherapy, 2007Co-Authors: Susan J. Schroeder, Gregor Blaha, Peter B. MooreAbstract:Negamycin, a small-molecule inhibitor of protein synthesis, binds the Haloarcula marismortui 50S ribosomal subunit at a single site formed by highly conserved RNA nucleotides near the cytosolic end of the nascent chain exit tunnel. The mechanism of antibiotic action and the function of this unexplored tunnel region remain intriguingly elusive.
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rna the first macromolecular catalyst the ribosome is a ribozyme
Trends in Biochemical Sciences, 2003Co-Authors: Thomas A Steitz, Peter B. MooreAbstract:Recently, the atomic structures of the large ribosomal subunit from Haloarcula marismortui and its complexes with substrates have been determined. These have provided exciting new insights into the principles of RNA structure, the mechanism of the peptidyl-transferase reaction and early events in the evolution of this RNA-protein complex assembly that is essential in all cells. The structures of the large subunit bound to a variety of antibiotics explain the effects of antibiotic resistance mutations and provide promise for the development of new antibiotics.
Jing Han - One of the best experts on this subject based on the ideXlab platform.
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Xiang H: Identification of the polyhydroxyalkanoate (PHA)-specific acetoacetyl-CoA reductase from multiple FabG paralogs in Haloarcula hispanica and reconstruction of PHA biosynthetic pathway in Haloferax volcanii
2013Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (�-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the �fabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea. Several haloarchaeal species belonging to the genera Haloferax, Haloarcula, Natrialba, and Haloquadratum are capable of synthesizing short-chain-length polyhydroxyalkanoates (SCL-PHAs) (6, 8, 14, 16), a large family of biopolymers with desirable biodegradability, biocompatibility, and thermoplastic features (31). Although the metabolic pathways of PHAs in bacteri
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Identification of the Polyhydroxyalkanoate (PHA)-Specific Acetoacetyl Coenzyme A Reductase among Multiple FabG Paralogs in Haloarcula hispanica and Reconstruction of the PHA Biosynthetic Pathway in Haloferax volcanii
Applied and environmental microbiology, 2009Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (beta-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the DeltafabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea.
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molecular characterization of the phaechm genes required for biosynthesis of poly 3 hydroxybutyrate in the extremely halophilic archaeon Haloarcula marismortui
Applied and Environmental Microbiology, 2007Co-Authors: Jing Han, Jian Zhou, Ligang Zhou, Hua XiangAbstract:Received 28 April 2007/Accepted 28 July 2007 Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of Archaea have not yet been experimentally investigated yet. In this study, we revealed that Haloarcula marismortui was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the phaEHm and phaCHm genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaCHm was revealed to be strongly bound with the PHB granules, but PhaEHm seemed not to be. Introduction of either the phaEHm or phaCHm gene into Haloarcula hispanica, which harbors highly homologous phaECHh genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the phaECHh genes in H. hispanica led to a complete loss of the PHA synthase activity. Complementation with phaECHm genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this phaEC-deleted haloarchaeon. These results indicated that the phaEC genes are required for biosynthesis of PHB and might encode an active PHA synthase in the Haloarcula species. Polyhydroxyalkanoates (PHAs) are a class of biodegradable polyesters of (R)-hydroxyalkanoates. These water-insoluble biopolymers are accumulated by a wide variety of bacteria and haloarchaea when the carbon source is available in excess but other nutrients are growth limiting (29). PHAs are attracting increasing attention due to their biodegradable, biocompatible, and thermoplastic features; thus, they are potential substitutes for petrochemical-derived plastics and can be used as packaging and biomedical materials, nonwoven fabrics, and flavor delivery agents (26). Nevertheless, the expensive cost for
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Molecular characterization of the phaECHm genes, required for biosynthesis of poly(3-hydroxybutyrate) in the extremely halophilic archaeon Haloarcula marismortui.
Applied and environmental microbiology, 2007Co-Authors: Jing Han, Jian Zhou, Ligang Zhou, Hua XiangAbstract:Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of Archaea have not yet been experimentally investigated yet. In this study, we revealed that Haloarcula marismortui was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the phaE(Hm) and phaC(Hm) genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaC(Hm) was revealed to be strongly bound with the PHB granules, but PhaE(Hm) seemed not to be. Introduction of either the phaE(Hm) or phaC(Hm) gene into Haloarcula hispanica, which harbors highly homologous phaEC(Hh) genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the phaEC(Hh) genes in H. hispanica led to a complete loss of the PHA synthase activity. Complementation with phaEC(Hm) genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this phaEC-deleted haloarchaeon. These results indicated that the phaEC genes are required for biosynthesis of PHB and might encode an active PHA synthase in the Haloarcula species.
Ligang Zhou - One of the best experts on this subject based on the ideXlab platform.
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Xiang H: Identification of the polyhydroxyalkanoate (PHA)-specific acetoacetyl-CoA reductase from multiple FabG paralogs in Haloarcula hispanica and reconstruction of PHA biosynthetic pathway in Haloferax volcanii
2013Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (�-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the �fabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea. Several haloarchaeal species belonging to the genera Haloferax, Haloarcula, Natrialba, and Haloquadratum are capable of synthesizing short-chain-length polyhydroxyalkanoates (SCL-PHAs) (6, 8, 14, 16), a large family of biopolymers with desirable biodegradability, biocompatibility, and thermoplastic features (31). Although the metabolic pathways of PHAs in bacteri
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Identification of the Polyhydroxyalkanoate (PHA)-Specific Acetoacetyl Coenzyme A Reductase among Multiple FabG Paralogs in Haloarcula hispanica and Reconstruction of the PHA Biosynthetic Pathway in Haloferax volcanii
Applied and environmental microbiology, 2009Co-Authors: Jing Han, Hailong Liu, Ligang Zhou, Hua XiangAbstract:Genome-wide analysis has revealed abundant FabG (beta-ketoacyl-ACP reductase) paralogs, with uncharacterized biological functions, in several halophilic archaea. In this study, we identified for the first time that the fabG1 gene, but not the other five fabG paralogs, encodes the polyhydroxyalkanoate (PHA)-specific acetoacetyl coenzyme A (acetoacetyl-CoA) reductase in Haloarcula hispanica. Although all of the paralogous fabG genes were actively transcribed, only disruption or knockout of fabG1 abolished PHA synthesis, and complementation of the DeltafabG1 mutant with the fabG1 gene restored both PHA synthesis capability and the NADPH-dependent acetoacetyl-CoA reductase activity. In addition, heterologous coexpression of the PHA synthase genes (phaEC) together with fabG1, but not its five paralogs, reconstructed the PHA biosynthetic pathway in Haloferax volcanii, a PHA-defective haloarchaeon. Taken together, our results indicate that FabG1 in H. hispanica, and possibly its counterpart in Haloarcula marismortui, has evolved the distinct function of supplying precursors for PHA biosynthesis, like PhaB in bacteria. Hence, we suggest the renaming of FabG1 in both genomes as PhaB, the PHA-specific acetoacetyl-CoA reductase of halophilic archaea.
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molecular characterization of the phaechm genes required for biosynthesis of poly 3 hydroxybutyrate in the extremely halophilic archaeon Haloarcula marismortui
Applied and Environmental Microbiology, 2007Co-Authors: Jing Han, Jian Zhou, Ligang Zhou, Hua XiangAbstract:Received 28 April 2007/Accepted 28 July 2007 Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of Archaea have not yet been experimentally investigated yet. In this study, we revealed that Haloarcula marismortui was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the phaEHm and phaCHm genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaCHm was revealed to be strongly bound with the PHB granules, but PhaEHm seemed not to be. Introduction of either the phaEHm or phaCHm gene into Haloarcula hispanica, which harbors highly homologous phaECHh genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the phaECHh genes in H. hispanica led to a complete loss of the PHA synthase activity. Complementation with phaECHm genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this phaEC-deleted haloarchaeon. These results indicated that the phaEC genes are required for biosynthesis of PHB and might encode an active PHA synthase in the Haloarcula species. Polyhydroxyalkanoates (PHAs) are a class of biodegradable polyesters of (R)-hydroxyalkanoates. These water-insoluble biopolymers are accumulated by a wide variety of bacteria and haloarchaea when the carbon source is available in excess but other nutrients are growth limiting (29). PHAs are attracting increasing attention due to their biodegradable, biocompatible, and thermoplastic features; thus, they are potential substitutes for petrochemical-derived plastics and can be used as packaging and biomedical materials, nonwoven fabrics, and flavor delivery agents (26). Nevertheless, the expensive cost for
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Molecular characterization of the phaECHm genes, required for biosynthesis of poly(3-hydroxybutyrate) in the extremely halophilic archaeon Haloarcula marismortui.
Applied and environmental microbiology, 2007Co-Authors: Jing Han, Jian Zhou, Ligang Zhou, Hua XiangAbstract:Although many haloarchaea produce biodegradable polyhydroxyalkanoates (PHAs), the genes involved in PHA synthesis in the domain of Archaea have not yet been experimentally investigated yet. In this study, we revealed that Haloarcula marismortui was able to accumulate poly(3-hydroxybutyrate) (PHB) up to 21% of cellular dry weight when cultured in a minimal medium with excessive glucose and identified the phaE(Hm) and phaC(Hm) genes, probably encoding two subunits of a class III PHA synthase. These two genes were adjacent and directed by a single promoter located 26 bp upstream of the transcriptional start site and were constitutively expressed under both nutrient-rich and -limited conditions. Interestingly, PhaC(Hm) was revealed to be strongly bound with the PHB granules, but PhaE(Hm) seemed not to be. Introduction of either the phaE(Hm) or phaC(Hm) gene into Haloarcula hispanica, which harbors highly homologous phaEC(Hh) genes, could enhance the PHB synthesis in the recombinant strains, while coexpression of the both genes always generated the highest PHB yield. Significantly, knockout of the phaEC(Hh) genes in H. hispanica led to a complete loss of the PHA synthase activity. Complementation with phaEC(Hm) genes, but not a single one, restored the capability of PHB accumulation as well as the PHA synthase activity in this phaEC-deleted haloarchaeon. These results indicated that the phaEC genes are required for biosynthesis of PHB and might encode an active PHA synthase in the Haloarcula species.
Thomas A Steitz - One of the best experts on this subject based on the ideXlab platform.
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Structures of Triacetyloleandomycin and Mycalamide A Bind to the Large Ribosomal Subunit of Haloarcula marismortui
Antimicrobial Agents and Chemotherapy, 2009Co-Authors: G. Gurel, Thomas A Steitz, Gregor Blaha, Peter B. MooreAbstract:Structures have been obtained for the complexes that triacetyloleandomycin and mycalamide A form with the large ribosomal subunit of Haloarcula marismortui. Triacetyloleandomycin binds in the nascent peptide tunnel and inhibits the activity of ribosomes by blocking the growth of the nascent peptide chain. Mycalamide A binds to the E site and inhibits protein synthesis by occupying the space normally occupied by the CCA end of E-site-bound tRNAs.
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crystal structure of the oxazolidinone antibiotic linezolid bound to the 50s ribosomal subunit
Journal of Medicinal Chemistry, 2008Co-Authors: Joseph A Ippolito, Peter B. Moore, Thomas A Steitz, Francois Franceschi, Zoltan F Kanyo, Deping Wang, Erin M DuffyAbstract:The oxazolidinone antibacterials target the 50S subunit of prokaryotic ribosomes. To gain insight into their mechanism of action, the crystal structure of the canonical oxazolidinone, linezolid, has been determined bound to the Haloarcula marismortui 50S subunit. Linezolid binds the 50S A-site, near the catalytic center, which suggests that inhibition involves competition with incoming A-site substrates. These results provide a structural basis for the discovery of improved oxazolidinones active against emerging drug-resistant clinical strains.
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on the structural basis of peptide bond formation and antibiotic resistance from atomic structures of the large ribosomal subunit
FEBS Letters, 2005Co-Authors: Thomas A SteitzAbstract:The atomic structures of the large ribosomal subunit from Haloarcula marismortui and its complexes with substrates and antibiotics have provided insights into the way the 3000 nucleotide 23S rRNA folds into a compact, specific structure and interacts with 27 ribosomal proteins as well as the structural basis of the peptidyl transferase reaction and its inhibition by antibiotics. The structure shows that the ribosome is indeed a ribozyme.
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rna the first macromolecular catalyst the ribosome is a ribozyme
Trends in Biochemical Sciences, 2003Co-Authors: Thomas A Steitz, Peter B. MooreAbstract:Recently, the atomic structures of the large ribosomal subunit from Haloarcula marismortui and its complexes with substrates have been determined. These have provided exciting new insights into the principles of RNA structure, the mechanism of the peptidyl-transferase reaction and early events in the evolution of this RNA-protein complex assembly that is essential in all cells. The structures of the large subunit bound to a variety of antibiotics explain the effects of antibiotic resistance mutations and provide promise for the development of new antibiotics.
