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Multiple Mechanisms for Copper Uptake by Methylosinus trichosporium OB3b in the Presence of Heterologous Methanobactin. mBio 2022; 13:e0223922. [PMID: 36129259 PMCID: PMC9601215 DOI: 10.1128/mbio.02239-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methanotrophs require copper for their activity as it plays a critical role in the oxidation of methane to methanol. To sequester copper, some methanotrophs secrete a copper-binding compound termed methanobactin (MB). MB, after binding copper, is reinternalized via a specific outer membrane TonB-dependent transporter (TBDT). Methylosinus trichosporium OB3b has two such TBDTs (MbnT1 and MbnT2) that enable M. trichosporium OB3b to take up not only its own MB (MB-OB3b) but also heterologous MB produced from other methanotrophs, e.g., MB of Methylocystis sp. strain SB2 (MB-SB2). Here, we show that uptake of copper in the presence of heterologous MB-SB2 can either be achieved by initiating transcription of mbnT2 or by using its own MB-OB3b to extract copper from MB-SB2. Transcription of mbnT2 is mediated by the N-terminal signaling domain of MbnT2 together with an extracytoplasmic function sigma factor and an anti-sigma factor encoded by mbnI2 and mbnR2, respectively. Deletion of mbnI2R2 or excision of the N-terminal region of MbnT2 abolished induction of mbnT2. However, copper uptake from MB-SB2 was still observed in M. trichosporium OB3b mutants that were defective in MbnT2 induction/function, suggesting another mechanism for uptake copper-loaded MB-SB2. Additional deletion of MB-OB3b synthesis genes in the M. trichosporium OB3b mutants defective in MbnT2 induction/function disrupted their ability to take up copper in the presence of MB-SB2, indicating a role of MB-OB3b in copper extraction from MB-SB2.
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Evidence for methanobactin "Theft" and novel chalkophore production in methanotrophs: impact on methanotrophic-mediated methylmercury degradation. THE ISME JOURNAL 2022; 16:211-220. [PMID: 34290379 PMCID: PMC8692452 DOI: 10.1038/s41396-021-01062-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/02/2021] [Accepted: 07/08/2021] [Indexed: 02/07/2023]
Abstract
Aerobic methanotrophy is strongly controlled by copper, and methanotrophs are known to use different mechanisms for copper uptake. Some methanotrophs secrete a modified polypeptide-methanobactin-while others utilize a surface-bound protein (MopE) and a secreted form of it (MopE*) for copper collection. As different methanotrophs have different means of sequestering copper, competition for copper significantly impacts methanotrophic activity. Herein, we show that Methylomicrobium album BG8, Methylocystis sp. strain Rockwell, and Methylococcus capsulatus Bath, all lacking genes for methanobactin biosynthesis, are not limited for copper by multiple forms of methanobactin. Interestingly, Mm. album BG8 and Methylocystis sp. strain Rockwell were found to have genes similar to mbnT that encodes for a TonB-dependent transporter required for methanobactin uptake. Data indicate that these methanotrophs "steal" methanobactin and such "theft" enhances the ability of these strains to degrade methylmercury, a potent neurotoxin. Further, when mbnT was deleted in Mm. album BG8, methylmercury degradation in the presence of methanobactin was indistinguishable from when MB was not added. Mc. capsulatus Bath lacks anything similar to mbnT and was unable to degrade methylmercury either in the presence or absence of methanobactin. Rather, Mc. capsulatus Bath appears to rely on MopE/MopE* for copper collection. Finally, not only does Mm. album BG8 steal methanobactin, it synthesizes a novel chalkophore, suggesting that some methanotrophs utilize both competition and cheating strategies for copper collection. Through a better understanding of these strategies, methanotrophic communities may be more effectively manipulated to reduce methane emissions and also enhance mercury detoxification in situ.
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MbnC is not required for the formation of the N-terminal oxazolone in the methanobactin from Methylosinus trichosporium OB3b. Appl Environ Microbiol 2021; 88:e0184121. [PMID: 34731053 PMCID: PMC8788703 DOI: 10.1128/aem.01841-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methanobactins (MBs) are ribosomally synthesized and post-translationally modified peptides (RiPPs) produced by methanotrophs for copper uptake. The post-translational modification that define MBs is the formation of two heterocyclic groups with associated thioamines from X-Cys dipeptide sequences. Both heterocyclic groups in the MB from Methylosinus trichosporium OB3b (MB-OB3b) are oxazolone groups. The precursor gene for MB-OB3b, mbnA, which is part of a gene cluster that contains both annotated and unannotated genes. One of those unannotated genes, mbnC, is found in all MB operons, and in conjunction with mbnB, is reported to be involved in the formation of both heterocyclic groups in all MBs. To determine the function of mbnC, a deletion mutation was constructed in M. trichosporium OB3b, and the MB produced from the ΔmbnC mutant was purified and structurally characterized by UV-visible absorption spectroscopy, mass spectrometry and solution NMR spectroscopy. MB-OB3b from ΔmbnC was missing the C-terminal Met and also found to contain a Pro and a Cys in place of the pyrrolidiny-oxazolone-thioamide group. These results demonstrate MbnC is required for the formation of the C-terminal pyrrolidinyl-oxazolone-thioamide group from the Pro-Cys dipeptide, but not for the formation of the N-terminal 3-methylbutanol-oxazolone-thioamide group from the N-terminal dipeptide Leu-Cys. IMPORTANCE A number of environmental and medical applications have been proposed for MBs, including bioremediation of toxic metals, nanoparticle formation, as well as for the treatment of copper- and iron-related diseases. However, before MBs can be modified and optimized for any specific application, the biosynthetic pathway for MB production must be defined. The discovery that mbnC is involved in the formation of the C-terminal oxazolone group with associated thioamide but not for the formation of the N-terminal oxazolone group with associated thioamide in M. trichosporium OB3b suggests the enzymes responsible for post-translational modification(s) of the two oxazolone groups are not identical.
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Two TonB-dependent transporters in Methylosinus trichosporium OB3b are responsible for uptake of different forms of methanobactin and are involved in the canonical 'copper switch'. Appl Environ Microbiol 2021; 88:e0179321. [PMID: 34669437 DOI: 10.1128/aem.01793-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Copper is an important component of methanotrophic physiology as it controls the expression and activity of alternative forms of methane monooxygenase (MMO). To collect copper, some methanotrophs secrete a chalkophore or copper-binding compound called methanobactin (MB). MB is a ribosomally synthesized post-translationally modified polypeptide (RiPP) that, after binding copper, is collected by MbnT, a TonB-dependent transporter (TBDT). Structurally different forms of MB have been characterized, and here we show that different forms of MB are collected by specific TBDTs. Further, we report that in the model methanotroph, Methylosinus trichosporium OB3b, expression of the TBDT required for uptake of a different MB made by Methylocystis sp. strain SB2 (MB-SB2), is induced in the presence of MB-SB2, suggesting that methanotrophs have developed specific machinery and regulatory systems to actively take up MB from other methanotrophs for copper collection. Moreover, the canonical "copper-switch" in Ms. trichosporium OB3b that controls expression of alternative MMOs is apparent if one of the two TBDTs required for MB-OB3b and MB-SB2 uptake is knocked out, but is disrupted if both TBDTs are knocked out. These data indicate that MB uptake, including the uptake of exogenous MB, plays an important role in the copper switch in M. trichosporium OB3b and thus overall activity. Based on these data, we propose a revised model for the "copper-switch" in this methanotroph that involves MB uptake. IMPORTANCE In this study, we demonstrate that different TonB-dependent transporters (TBDTs) in the model methanotroph Methylosinus trichosporium OB3b are responsible for uptake of either endogenous MB or exogenous MB. Interestingly, the presence of exogenous MB induces expression of its specific TBDT in M. trichosporium OB3b, suggesting that this methanotroph is able to actively take up MB produced by others. This work contributes to our understanding of how microbes collect and compete for copper, and also helps inform how such uptake coordinates the expression of different forms of methane monooxygenase. Such studies are likely to be very important to develop a better understanding of methanotrophic interactions via synthesis and secretion of secondary metabolites such as methanobactin and thus provide additional means whereby these microbes can be manipulated for a variety of environmental and industrial purposes.
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Abstract
Methanobactins (MBs) are small (<1,300-Da) posttranslationally modified copper-binding peptides and represent the extracellular component of a copper acquisition system in some methanotrophs. Interestingly, MBs can bind a range of metal ions, with some being reduced after binding, e.g., Cu2+ reduced to Cu+. Other metal ions, however, are bound but not reduced, e.g., K+. The source of electrons for selective metal ion reduction has been speculated to be water but never empirically shown. Here, using H218O, we show that when MBs from Methylocystis sp. strain SB2 (MB-SB2) and Methylosinus trichosporium OB3b (MB-OB3) were incubated in the presence of either Au3+, Cu2, or Ag+, 18,18O2 and free protons were released. No 18,18O2 production was observed in the presence of either MB-SB2 or MB-OB3b alone, gold alone, copper alone, or silver alone or when K+ or Mo2+ was incubated with MB-SB2. In contrast to MB-OB3b, MB-SB2 binds Fe3+ with an N2S2 coordination and will also reduce Fe3+ to Fe2+. Iron reduction was also found to be coupled to the oxidation of 2H2O and the generation of O2. MB-SB2 will also couple Hg2+, Ni2+, and Co2+ reduction to the oxidation of 2H2O and the generation of O2, but MB-OB3b will not, ostensibly as MB-OB3b binds but does not reduce these metal ions. To determine if the O2 generated during metal ion reduction by MB could be coupled to methane oxidation, 13CH4 oxidation by Methylosinus trichosporium OB3b was monitored under anoxic conditions. The results demonstrate that O2 generation from metal ion reduction by MB-OB3b can support methane oxidation. IMPORTANCE The discovery that MB will couple the oxidation of H2O to metal ion reduction and the release of O2 suggests that methanotrophs expressing MB may be able to maintain their activity under hypoxic/anoxic conditions through the “self-generation” of dioxygen required for the initial oxidation of methane to methanol. Such an ability may be an important factor in enabling methanotrophs to not only colonize the oxic-anoxic interface where methane concentrations are highest but also tolerate significant temporal fluctuations of this interface. Given that genomic surveys often show evidence of aerobic methanotrophs within anoxic zones, the ability to express MB (and thereby generate dioxygen) may be an important parameter in facilitating their ability to remove methane, a potent greenhouse gas, before it enters the atmosphere.
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Enhancement of nitrous oxide emissions in soil microbial consortia via copper competition between proteobacterial methanotrophs and denitrifiers. Appl Environ Microbiol 2020; 87:e0230120. [PMID: 33355098 DOI: 10.1128/aem.02301-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Unique means of copper scavenging have been identified in proteobacterial methanotrophs, particularly the use of methanobactin, a novel ribosomally synthesized post-translationally modified polypeptide that binds copper with very high affinity. The possibility that copper sequestration strategies of methanotrophs may interfere with copper uptake of denitrifiers in situ and thereby enhance N2O emissions was examined using a suite of laboratory experiments performed with rice paddy microbial consortia. Addition of purified methanobactin from Methylosinus trichosporium OB3b to denitrifying rice paddy soil microbial consortia resulted in substantially increased N2O production, with more pronounced responses observed for soils with lower copper content. The N2O emission-enhancing effect of the soil's native mbnA-expressing Methylocystaceae methanotrophs on the native denitrifiers was then experimentally verified with a Methylocystaceae-dominant chemostat culture prepared from a rice paddy microbial consortium as the inoculum. Lastly, with microcosms amended with varying cell numbers of methanobactin-producing Methylosinus trichosporium OB3b before CH4 enrichment, microbiomes with different ratios of methanobactin-producing Methylocystaceae to gammaproteobacterial methanotrophs incapable of methanobactin production were simulated. Significant enhancement of N2O production from denitrification was evident in both Methylocystaceae-dominant and Methylococcaceae-dominant enrichments, albeit to a greater extent in the former, signifying the comparative potency of methanobactin-mediated copper sequestration while implying the presence of alternative copper abstraction mechanisms for Methylococcaceae These observations support that copper-mediated methanotrophic enhancement of N2O production from denitrification is plausible where methanotrophs and denitrifiers cohabit.IMPORTANCE Proteobacterial methanotrophs, groups of microorganisms that utilize methane as source of energy and carbon, have been known to utilize unique mechanisms to scavenge copper, namely utilization of methanobactin, a polypeptide that binds copper with high affinity and specificity. Previously the possibility that copper sequestration by methanotrophs may lead to alteration of cuproenzyme-mediated reactions in denitrifiers and consequently increase emission of potent greenhouse gas N2O has been suggested in axenic and co-culture experiments. Here, a suite of experiments with rice paddy soil slurry cultures with complex microbial compositions were performed to corroborate that such copper-mediated interplay may actually take place in environments co-habited by diverse methanotrophs and denitrifiers. As spatial and temporal heterogeneity allow for spatial coexistence of methanotrophy (aerobic) and denitrification (anaerobic) in soils, the results from this study suggest that this previously unidentified mechanism of N2O production may account for significant proportion of N2O efflux from agricultural soils.
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7
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Semrau JD, DiSpirito AA. Methanobactin: A Novel Copper-Binding Compound Produced by Methanotrophs. ACTA ACUST UNITED AC 2019. [DOI: 10.1007/978-3-030-23261-0_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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8
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Mahanta N, Szantai-Kis DM, Petersson EJ, Mitchell DA. Biosynthesis and Chemical Applications of Thioamides. ACS Chem Biol 2019; 14:142-163. [PMID: 30698414 PMCID: PMC6404778 DOI: 10.1021/acschembio.8b01022] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Thioamidation as a posttranslational modification is exceptionally rare, with only a few reported natural products and exactly one known protein example (methyl-coenzyme M reductase from methane-metabolizing archaea). Recently, there has been significant progress in elucidating the biosynthesis and function of several thioamide-containing natural compounds. Separate developments in the chemical installation of thioamides into peptides and proteins have enabled cell biology and biophysical studies to advance the current understanding of natural thioamides. This review highlights the various strategies used by Nature to install thioamides in peptidic scaffolds and the potential functions of this rare but important modification. We also discuss synthetic methods used for the site-selective incorporation of thioamides into polypeptides with a brief discussion of the physicochemical implications. This account will serve as a foundation for the further study of thioamides in natural products and their various applications.
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Affiliation(s)
| | - D Miklos Szantai-Kis
- Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine , University of Pennsylvania , 3700 Hamilton Walk , Philadelphia , Pennsylvania 19104 , United States
| | - E James Petersson
- Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine , University of Pennsylvania , 3700 Hamilton Walk , Philadelphia , Pennsylvania 19104 , United States
- Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104 , United States
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9
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Park YJ, Kenney GE, Schachner LF, Kelleher NL, Rosenzweig AC. Repurposed HisC Aminotransferases Complete the Biosynthesis of Some Methanobactins. Biochemistry 2018; 57:3515-3523. [PMID: 29694778 PMCID: PMC6019534 DOI: 10.1021/acs.biochem.8b00296] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Methanobactins (Mbns) are ribosomally produced, post-translationally modified bacterial natural products with a high affinity for copper. MbnN, a pyridoxal 5'-phosphate-dependent aminotransferase, performs a transamination reaction that is the last step in the biosynthesis of Mbns produced by several Methylosinus species. Our bioinformatic analyses indicate that MbnNs likely derive from histidinol-phosphate aminotransferases (HisCs), which play a key role in histidine biosynthesis. A comparison of the HisC active site with the predicted MbnN structure suggests that MbnN's active site is altered to accommodate the larger and more hydrophobic substrates necessary for Mbn biosynthesis. Moreover, we have confirmed that MbnN is capable of catalyzing the final transamination step in Mbn biosynthesis in vitro and in vivo. We also demonstrate that without this final modification, Mbn exhibits significantly decreased stability under physiological conditions. An examination of other Mbns and Mbn operons suggests that N-terminal protection of this family of natural products is of critical importance and that several different means of N-terminal stabilization have evolved independently in Mbn subfamilies.
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Affiliation(s)
- Yun Ji Park
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Grace E. Kenney
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Luis F. Schachner
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Neil L. Kelleher
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Amy C. Rosenzweig
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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10
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Abstract
Copper-binding metallophores, or chalkophores, play a role in microbial copper homeostasis that is analogous to that of siderophores in iron homeostasis. The best-studied chalkophores are members of the methanobactin (Mbn) family-ribosomally produced, posttranslationally modified natural products first identified as copper chelators responsible for copper uptake in methane-oxidizing bacteria. To date, Mbns have been characterized exclusively in those species, but there is genomic evidence for their production in a much wider range of bacteria. This review addresses the current state of knowledge regarding the function, biosynthesis, transport, and regulation of Mbns. While the roles of several proteins in these processes are supported by substantial genetic and biochemical evidence, key aspects of Mbn manufacture, handling, and regulation remain unclear. In addition, other natural products that have been proposed to mediate copper uptake as well as metallophores that have biologically relevant roles involving copper binding, but not copper uptake, are discussed.
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Affiliation(s)
- Grace E Kenney
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA; ,
| | - Amy C Rosenzweig
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA; ,
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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11
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Kenney GE, Dassama LMK, Pandelia ME, Gizzi AS, Martinie RJ, Gao P, DeHart CJ, Schachner LF, Skinner OS, Ro SY, Zhu X, Sadek M, Thomas PM, Almo SC, Bollinger JM, Krebs C, Kelleher NL, Rosenzweig AC. The biosynthesis of methanobactin. Science 2018; 359:1411-1416. [PMID: 29567715 DOI: 10.1126/science.aap9437] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 02/07/2018] [Indexed: 11/02/2022]
Abstract
Metal homeostasis poses a major challenge to microbes, which must acquire scarce elements for core metabolic processes. Methanobactin, an extensively modified copper-chelating peptide, was one of the earliest natural products shown to enable microbial acquisition of a metal other than iron. We describe the core biosynthetic machinery responsible for the characteristic posttranslational modifications that grant methanobactin its specificity and affinity for copper. A heterodimer comprising MbnB, a DUF692 family iron enzyme, and MbnC, a protein from a previously unknown family, performs a dioxygen-dependent four-electron oxidation of the precursor peptide (MbnA) to install an oxazolone and an adjacent thioamide, the characteristic methanobactin bidentate copper ligands. MbnB and MbnC homologs are encoded together and separately in many bacterial genomes, suggesting functions beyond their roles in methanobactin biosynthesis.
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Affiliation(s)
- Grace E Kenney
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Laura M K Dassama
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | | | - Anthony S Gizzi
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ryan J Martinie
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Peng Gao
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Caroline J DeHart
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Luis F Schachner
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Owen S Skinner
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Soo Y Ro
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Xiao Zhu
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Monica Sadek
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Paul M Thomas
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Steven C Almo
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - J Martin Bollinger
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Neil L Kelleher
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Amy C Rosenzweig
- Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
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12
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Ro SY, Rosenzweig AC. Recent Advances in the Genetic Manipulation of Methylosinus trichosporium OB3b. Methods Enzymol 2018; 605:335-349. [PMID: 29909832 DOI: 10.1016/bs.mie.2018.02.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methanotrophic bacteria utilize methane as their sole carbon and energy source. Studies of the model Type II methanotroph Methylosinus trichosporium OB3b have provided insight into multiple aspects of methanotrophy, including methane assimilation, copper accumulation, and metal-dependent gene expression. Development of genetic tools for chromosomal editing was crucial for advancing these studies. Recent interest in methanotroph metabolic engineering has led to new protocols for genetic manipulation of methanotrophs that are effective and simple to use. We have incorporated these newer molecular tools into existing protocols for Ms. trichosporium OB3b. The modifications include additional shuttle and replicative plasmids as well as improved gene delivery and genotyping. The methods described here render gene editing in Ms. trichosporium OB3b efficient and accessible.
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Affiliation(s)
- Soo Y Ro
- Northwestern University, Evanston, IL, United States
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13
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Kenney GE, Rosenzweig AC. Methanobactins: Maintaining copper homeostasis in methanotrophs and beyond. J Biol Chem 2018; 293:4606-4615. [PMID: 29348173 PMCID: PMC5880147 DOI: 10.1074/jbc.tm117.000185] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Methanobactins (Mbns) are ribosomally produced, post-translationally modified natural products that bind copper with high affinity and specificity. Originally identified in methanotrophic bacteria, which have a high need for copper, operons encoding these compounds have also been found in many non-methanotrophic bacteria. The proteins responsible for Mbn biosynthesis include several novel enzymes. Mbn transport involves export through a multidrug efflux pump and re-internalization via a TonB-dependent transporter. Release of copper from Mbn and the molecular basis for copper regulation of Mbn production remain to be elucidated. Future work is likely to result in the identification of new enzymatic chemistry, opportunities for bioengineering and drug targeting of copper metabolism, and an expanded understanding of microbial metal homeostasis.
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Affiliation(s)
- Grace E Kenney
- Departments of Molecular Biosciences, Evanston, Illinois 60208
| | - Amy C Rosenzweig
- Departments of Molecular Biosciences, Evanston, Illinois 60208; Chemistry, Northwestern University, Evanston, Illinois 60208.
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14
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Abstract
Aerobic methanotrophs have long been known to play a critical role in the global carbon cycle, being capable of converting methane to biomass and carbon dioxide. Interestingly, these microbes exhibit great sensitivity to copper and rare-earth elements, with the expression of key genes involved in the central pathway of methane oxidation controlled by the availability of these metals. That is, these microbes have a "copper switch" that controls the expression of alternative methane monooxygenases and a "rare-earth element switch" that controls the expression of alternative methanol dehydrogenases. Further, it has been recently shown that some methanotrophs can detoxify inorganic mercury and demethylate methylmercury; this finding is remarkable, as the canonical organomercurial lyase does not exist in these methanotrophs, indicating that a novel mechanism is involved in methylmercury demethylation. Here, we review recent findings on methanotrophic interactions with metals, with a particular focus on these metal switches and the mechanisms used by methanotrophs to bind and sequester metals.
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15
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Abstract
Copper is essential for most organisms as a cofactor for key enzymes involved in fundamental processes such as respiration and photosynthesis. However, copper also has toxic effects in cells, which is why eukaryotes and prokaryotes have evolved mechanisms for safe copper handling. A new family of bacterial proteins uses a Cys-rich four-helix bundle to safely store large quantities of Cu(I). The work leading to the discovery of these proteins, their properties and physiological functions, and how their presence potentially impacts the current views of bacterial copper handling and use are discussed in this review.
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Affiliation(s)
- Christopher Dennison
- Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
| | - Sholto David
- Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Jaeick Lee
- Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
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16
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Methanobactin from Methylosinus trichosporium OB3b inhibits N 2O reduction in denitrifiers. ISME JOURNAL 2018; 12:2086-2089. [PMID: 29330532 DOI: 10.1038/s41396-017-0022-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 11/09/2017] [Accepted: 11/17/2017] [Indexed: 11/09/2022]
Abstract
Methanotrophs synthesize methanobactin, a secondary metabolite that binds copper with an unprecedentedly high affinity. Such a strategy may provide methanotrophs a "copper monopoly" that can inhibit the activity of copper-containing enzymes of other microbes, e.g., copper-dependent N2O reductases. Here, we show that methanobactin from Methylosinus trichosporium OB3b inhibited N2O reduction in denitrifiers. When Pseudomonas stutzeri DCP-Ps1 was incubated in cocultures with M. trichosporium OB3b or with purified methanobactin from M. trichosporium OB3b, stoichiometric N2O production was observed from NO3- reduction, whereas no significant N2O accumulation was observed in cocultures with a mutant defective in methanobactin production. Copper uptake by P. stutzeri DCP-Ps1 was inhibited by the presence of purified methanobactin, leading to a significant downregulation of nosZ transcription. Similar findings were observed with three other denitrifier strains. These results suggest that in situ stimulation of methanotrophs can inadvertently increase N2O emissions, with the potential for increasing net greenhouse gas emissions.
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Wang L, Zhu M, Zhang Q, Zhang X, Yang P, Liu Z, Deng Y, Zhu Y, Huang X, Han L, Li S, He J. Diisonitrile Natural Product SF2768 Functions As a Chalkophore That Mediates Copper Acquisition in Streptomyces thioluteus. ACS Chem Biol 2017; 12:3067-3075. [PMID: 29131568 DOI: 10.1021/acschembio.7b00897] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A nonribosomal peptide synthetase (NRPS) gene cluster (sfa) was identified in Streptomyces thioluteus to direct the biosynthesis of the diisonitrile antibiotic SF2768. Its biosynthetic pathway was reasonably proposed based on bioinformatics analysis, metabolic profiles of mutants, and the elucidation of the intermediate and shunt product structures. Bioinformatics-based alignment found a putative ATP-binding cassette (ABC) transporter related to iron import within the biosynthetic gene cluster, which implied that the product might be a siderophore. However, characterization of the metal-binding properties by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), metal-ligand titration, thin-layer chromatography (TLC), and chrome azurol S (CAS) assays revealed that the final product SF2768 and its diisonitrile derivatives specifically bind copper, rather than iron, to form stable complexes. Inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed that the intracellular cupric content of S. thioluteus significantly increased upon incubation with the copper-SF2768 complex, direct evidence for the copper acquisition function of SF2768. Further in vivo functional characterization of the transport elements for the copper-SF2768 complexes not only confirmed the chalkophore identity of the compound but also gave initial clues into the copper uptake mechanism of this nonmethanotrophic microorganism.
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Affiliation(s)
- Lijuan Wang
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Mengyi Zhu
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Qingbo Zhang
- CAS
Key Laboratory of Tropical Marine Bio-resources and Ecology, RNAM
Center for Marine Microbiology, Guangdong Key Laboratory of Marine
Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, People’s Republic of China
| | - Xu Zhang
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Panlei Yang
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Zihui Liu
- State
Key Laboratory of Agricultural Microbiology, College of Science, Huazhong Agricultural University, Wuhan 430070, China
| | - Yun Deng
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Yiguang Zhu
- CAS
Key Laboratory of Tropical Marine Bio-resources and Ecology, RNAM
Center for Marine Microbiology, Guangdong Key Laboratory of Marine
Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, People’s Republic of China
| | - Xueshi Huang
- Institute
of Microbial Pharmaceuticals, College of Life and Health Sciences, Northeastern University, Shenyang 110819, China
| | - Li Han
- Institute
of Microbial Pharmaceuticals, College of Life and Health Sciences, Northeastern University, Shenyang 110819, China
| | - Shengqing Li
- State
Key Laboratory of Agricultural Microbiology, College of Science, Huazhong Agricultural University, Wuhan 430070, China
| | - Jing He
- National
Key Laboratory of Agricultural Microbiology, College of Life Science
and Technology, Huazhong Agricultural University, Wuhan 430070, China
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Gu W, Farhan Ul Haque M, Semrau JD. Characterization of the role of copCD in copper uptake and the ‘copper-switch’ in Methylosinus trichosporium OB3b. FEMS Microbiol Lett 2017; 364:3796321. [DOI: 10.1093/femsle/fnx094] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/03/2017] [Indexed: 11/13/2022] Open
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