Methanobactin from methanotrophs: genetics, structure, function and potential applications

Abstract

Aerobic methane-oxidizing bacteria of the Alphaproteobacteria have been found to express a novel ribosomally synthesized post-translationally modified polypeptide (RiPP) termed methanobactin (MB). The primary function of MB in these microbes appears to be for copper uptake, but MB has been shown to have multiple capabilities, including oxidase, superoxide dismutase and hydrogen peroxide reductase activities, the ability to detoxify mercury species, as well as acting as an antimicrobial agent. Herein, we describe the diversity of known MBs as well as the genetics underlying MB biosynthesis. We further propose based on bioinformatics analyses that some methanotrophs may produce novel forms of MB that have yet to be characterized. We also discuss recent findings documenting that MBs play an important role in controlling copper availability to the broader microbial community, and as a result can strongly affect the activity of microbes that require copper for important enzymatic transformations, e.g. conversion of nitrous oxide to dinitrogen. Finally, we describe procedures for the detection/purification of MB, as well as potential medical and industrial applications of this intriguing RiPP.

Towards a unified understanding of the copper sites in particulate methane monooxygenase: an X-ray absorption spectroscopic investigation

“…[1][2][3][4] Alternatively, methanotrophic bacteria 5 have evolved two genetically unrelated enzymes to catalyze methane to methanol conversion under ambient conditions: soluble and particulate methane monooxygenase (sMMO and pMMO, respectively). 6 sMMO features a well-characterized diiron active site, 7,8 and while pMMO is generally accepted as a copper enzyme, 6,9,10 the identity of its catalytic copper cofactor has proved far more elusive, severely impeding our mechanistic understanding of this important enzyme. 11 Much of the literature over the past two decades has focused on the possibility of a multinuclear copper active site, with the main proposals involving a tricopper site in the PmoA subunit and a dicopper site in the PmoB subunit (Fig.…”

Detoxification, Active Uptake, and Intracellular Accumulation of Chromium Species by a Methane-Oxidizing Bacterium

“…Methanotrophs are known to bind and transform a range of toxic metals and metalloids in addition to chromium. The alphaproteobacterial methanotrophs, such as Methylosinus trichosporium OB3b, produce a range of structurally related copper-scavenging molecules termed methanobactins ( 22 ). Methanobactin-bound copper is in the +1 oxidation state; binding of Cu(II) to methanobactin results in its reduction to Cu(I) ( 23 ), possibly by electrons derived from water ( 22 ).…”

“…The alphaproteobacterial methanotrophs, such as Methylosinus trichosporium OB3b, produce a range of structurally related copper-scavenging molecules termed methanobactins ( 22 ). Methanobactin-bound copper is in the +1 oxidation state; binding of Cu(II) to methanobactin results in its reduction to Cu(I) ( 23 ), possibly by electrons derived from water ( 22 ). Methanobactin is able to bind a wide range of cations; a subset of these, including Hg(II) and Au(III), undergo reduction upon binding, in a similar manner to copper, to give metallic mercury and metallic gold nanoparticles, respectively ( 24 – 27 ).…”

Biomedical Applications of Biomolecules Isolated from Methanotrophic Bacteria in Wastewater Treatment Systems

“…Methanobactin acts as a chelating agent with the ability to bind to copper, mercury and gold particles [86]. This is especially important as the ability of reducing gold has successfully generated gold nanoparticles that have many biomedical applications.…”