Structure and Protein–Protein Interactions of Methanol Dehydrogenase from <i>Methylococcus capsulatus</i> (Bath)

Culpepper, Megen A.; Rosenzweig, Amy C.

doi:10.1021/bi500850j

Cited by 45 publications

(69 citation statements)

References 70 publications

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“…Cerium, however, had little effect on mxaF or mxaI expression under pMMO-expressing conditions, i.e., when 10 M copper was present. Such findings support earlier conclusions that the pMMO forms a supercomplex with the Mxa-MeDH (19,20) and that this complex is critical for the oxidation of methane in methanotrophs under pMMO-expressing conditions, i.e., in the presence of copper. Our findings suggest, however, that Mxa-MeDH is not essential in sMMO-expressing conditions; rather, Xox-MeDH is sufficient for the further oxidation of methanol.…”

Section: Discussionsupporting

confidence: 91%

“…Cryoelectron microscopy work done by Myronova et al (19) indicated that the PQQ-linked MeDH likely forms a "cap" to the pMMO "body," with the PQQ-linked MeDH residing in the periplasmic space. Subsequent studies support this conclusion and indicate that the PQQ-linked MeDH and pMMO supercomplex is anchored via the intracytoplasmic membranes (20). Other research also suggests that electron transfer from the PQQ-linked MeDH to pMMO may occur in vivo (21,22).…”

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confidence: 88%

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Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

Haque

Kalidass

Bandow

et al. 2015

Appl Environ Microbiol

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bMethanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a "copper switch." At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO. It is well known that microorganisms have diverse mechanisms to sense and respond to metals in their environment. These mechanisms typically include strategies to regulate gene expression in response to the presence or absence of metals such as copper, zinc, iron, manganese, arsenic, and mercury (see, for example, references 1, 2, 3 and 4). One such phenomenon is the "copper switch" in methanotrophs. That is, these microbes utilize methane as their sole growth substrate but have two different monooxygenases for the initial oxidation of methane to methanol. One, the particulate methane monooxygenase (pMMO), is found in the intracytoplasmic membranes of these microbes, and its expression and activity increases with increasing availability of copper. The second, the soluble methane monooxygenase (sMMO), is found in the cytoplasm and is only expressed when copper is unavailable (5). These two forms of MMO have very different structures, activities, and substrate ranges (5-14), and so careful consideration of the form of MMO expressed is critical for understanding methanotrophic ecology, as well for various applications of methanotrophy, including the removal of chlorinated solvents and methane, a potent greenhouse gas (5, 10, 12, 15).Further, interest in the commercial application of methanotrophy has dramatically accelerated in recent years, in part due to increased methane supplies given advances in hydraulic fracturing of shale formations. As a result, methane prices have become quite low, with the wellhead price of natural gas dropping fro...

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Section: Discussionsupporting

confidence: 91%

mentioning

confidence: 88%

Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

Haque

Kalidass

Bandow

et al. 2015

Appl Environ Microbiol

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“…In this study, we demonstrated the existence of a lanthanide- (28,40), both MxaFI and XoxF must be able to form such a complex.…”

Section: Discussionmentioning

confidence: 61%

XoxF Acts as the Predominant Methanol Dehydrogenase in the Type I Methanotroph Methylomicrobium buryatense

2016

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Many methylotrophic taxa harbor two distinct methanol dehydrogenase (MDH) systems for oxidizing methanol to formaldehyde: the well-studied calcium-dependent MxaFI type and the more recently discovered lanthanide-containing XoxF type. MxaFI has traditionally been accepted as the major functional MDH in bacteria that contain both enzymes. However, in this study, we present evidence that, in a type I methanotroph, Methylomicrobium buryatense, XoxF is likely the primary functional MDH in the environment. The addition of lanthanides increases xoxF expression and greatly reduces mxa expression, even under conditions in which calcium concentrations are almost 100-fold higher than lanthanide concentrations. Mutations in genes encoding the MDH enzymes validate our finding that XoxF is the major functional MDH, as XoxF mutants grow more poorly than MxaFI mutants under unfavorable culturing conditions. In addition, mutant and transcriptional analyses demonstrate that the lanthanide-dependent MDH switch operating in methanotrophs is mediated in part by the orphan response regulator MxaB, whose gene transcription is itself lanthanide responsive. IMPORTANCEAerobic methanotrophs, bacteria that oxidize methane for carbon and energy, require a methanol dehydrogenase enzyme to convert methanol into formaldehyde. The calcium-dependent enzyme MxaFI has been thought to primarily carry out methanol oxidation in methanotrophs. Recently, it was discovered that XoxF, a lanthanide-containing enzyme present in most methanotrophs, can also oxidize methanol. In a methanotroph with both MxaFI and XoxF, we demonstrate that lanthanides transcriptionally control genes encoding the two methanol dehydrogenases, in part by controlling expression of the response regulator MxaB. Lanthanides are abundant in the Earth's crust, and we demonstrate that micromolar amounts of lanthanides are sufficient to suppress MxaFI expression. Thus, we present evidence that XoxF acts as the predominant methanol dehydrogenase in a methanotroph.A n increasing surplus in the global methane budget exists due to human activity. The industrial use of microorganisms to convert methane into useful chemicals or biofuels represents one way to mitigate atmospheric methane (1, 2). Methanotrophs, or methane-oxidizing bacteria, utilize methane as their carbon and energy source and are prime candidates for the industrial bioconversion of methane (1). Renewed interest in the industrial use of methanotrophs has come about partially because of the discovery of rapidly growing strains and new tools for genetic manipulation, allowing for fast-paced metabolic engineering (3, 4). The success of metabolic engineering strategies in these methanotrophs depends upon a strong foundation of knowledge concerning the metabolic pathways that methanotrophs employ, both in the laboratory and in their natural environments, and an understanding of how various branches of metabolic pathways are regulated.The majority of methanotrophs have two systems for oxidizing methane to methanol: the parti...

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“…There are often multiple copies of these pmo genes in methanotrophs (78,79). Recent studies have shown that native pMMO forms a complex with methanol dehydrogenase (MeDH), which may supply electrons to the pMMO (80,81), similar to what has been found for the hydroxylamine oxidoreductase and ammonia monooxygenase redox couples (82)(83)(84)(85).…”

Section: Physiology and Biochemistry Of Methanotrophsmentioning

confidence: 87%

“…This was not totally unexpected, however: considering that the pMMO is localized in the intracytoplasmic membranes, then greater expression and activity of pMMO would logically require more of these membranes. More surprisingly, however, it was recently discovered that pMMO and the PQQ-linked MeDH encoded by the mxa operon form a supercomplex anchored in the intracytoplasmic membranes and that electron transfer from the PQQ-linked MeDH to pMMO in vivo may drive the oxidation of methane (80,81). In support of the latter finding, it was recently found that not only does expression of pmo genes increase with increasing copper, but that of genes in the mxa operon does so as well (91).…”

Section: The "Copper Switch" In Methanotrophsmentioning

confidence: 99%

Methanobactin and the Link between Copper and Bacterial Methane Oxidation

DiSpirito

Semrau

Murrell

et al. 2016

Microbiol Mol Biol Rev

127

157

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SUMMARYMethanobactins (mbs) are low-molecular-mass (<1,200 Da) copper-binding peptides, or chalkophores, produced by many methane-oxidizing bacteria (methanotrophs). These molecules exhibit similarities to certain iron-binding siderophores but are expressed and secreted in response to copper limitation. Structurally, mbs are characterized by a pair of heterocyclic rings with associated thioamide groups that form the copper coordination site. One of the rings is always an oxazolone and the second ring an oxazolone, an imidazolone, or a pyrazinedione moiety. The mb molecule originates from a peptide precursor that undergoes a series of posttranslational modifications, including (i) ring formation, (ii) cleavage of a leader peptide sequence, and (iii) in some cases, addition of a sulfate group. Functionally, mbs represent the extracellular component of a copper acquisition system. Consistent with this role in copper acquisition, mbs have a high affinity for copper ions. Following binding, mbs rapidly reduce Cu2+to Cu1+. In addition to binding copper, mbs will bind most transition metals and near-transition metals and protect the host methanotroph as well as other bacteria from toxic metals. Several other physiological functions have been assigned to mbs, based primarily on their redox and metal-binding properties. In this review, we examine the current state of knowledge of this novel type of metal-binding peptide. We also explore its potential applications, how mbs may alter the bioavailability of multiple metals, and the many roles mbs may play in the physiology of methanotrophs.

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Structure and Protein–Protein Interactions of Methanol Dehydrogenase from Methylococcus capsulatus (Bath)

Cited by 45 publications

References 70 publications

Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

XoxF Acts as the Predominant Methanol Dehydrogenase in the Type I Methanotroph Methylomicrobium buryatense

Methanobactin and the Link between Copper and Bacterial Methane Oxidation

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