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The biosynthesis of methanobactin.

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.

SUBMITTER: Kenney GE

PROVIDER: S-EPMC5944852 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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The biosynthesis of methanobactin.

Kenney Grace E GE Dassama Laura M K LMK Pandelia Maria-Eirini ME Gizzi Anthony S AS Martinie Ryan J RJ Gao Peng P DeHart Caroline J CJ Schachner Luis F LF Skinner Owen S OS Ro Soo Y SY Zhu Xiao X Sadek Monica M Thomas Paul M PM Almo Steven C SC Bollinger J Martin JM Krebs Carsten C Kelleher Neil L NL Rosenzweig Amy C AC

Science (New York, N.Y.) 20180301 6382

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, ...[more]

PMID: 29567715

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Project description:Microbial production of the neurotoxin methylmercury (MeHg) is a significant health and environmental concern, as it can bioaccumulate and biomagnify in the food web. A chalkophore or a copper-binding compound, termed methanobactin (MB), has been shown to form strong complexes with mercury [as Hg(II)] and also enables some methanotrophs to degrade MeHg. It is unknown, however, if Hg(II) binding with MB can also impede Hg(II) methylation by other microbes. Contrary to expectations, MB produced by the methanotroph Methylosinus trichosporium OB3b (OB3b-MB) enhanced the rate and efficiency of Hg(II) methylation more than that observed with thiol compounds (such as cysteine) by the mercury-methylating bacteria Desulfovibrio desulfuricans ND132 and Geobacter sulfurreducens PCA. Compared to no-MB controls, OB3b-MB decreased the rates of Hg(II) sorption and internalization, but increased methylation by 5- to 7-fold, suggesting that Hg(II) complexation with OB3b-MB facilitated exchange and internal transfer of Hg(II) to the HgcAB proteins required for methylation. Conversely, addition of excess amounts of OB3b-MB or a different form of MB from Methylocystis strain SB2 (SB2-MB) inhibited Hg(II) methylation, likely due to greater binding of Hg(II). Collectively, our results underscore the complex roles of microbial exogenous metal-scavenging compounds in controlling net production and bioaccumulation of MeHg in the environment.IMPORTANCE Some anaerobic microorganisms convert inorganic mercury (Hg) into the neurotoxin methylmercury, which can bioaccumulate and biomagnify in the food web. While the genetic basis of microbial mercury methylation is known, factors that control net methylmercury production in the environment are still poorly understood. Here, it is shown that mercury methylation can be substantially enhanced by one form of an exogenous copper-binding compound (methanobactin) produced by some methanotrophs, but not by another. This novel finding illustrates that complex interactions exist between microbes and that these interactions can potentially affect the net production of methylmercury in situ.

Dataset Information

The biosynthesis of methanobactin.

Publications

The biosynthesis of methanobactin.

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