Summary: Ammonia monooxygenase
Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.
This is the Wikipedia entry entitled "Methane monooxygenase". More...
The Wikipedia text that you see displayed here is a download from Wikipedia. This means that the information we display is a copy of the information from the Wikipedia database. The button next to the article title ("Edit Wikipedia article") takes you to the edit page for the article directly within Wikipedia. You should be aware you are not editing our local copy of this information. Any changes that you make to the Wikipedia article will not be displayed here until we next download the article from Wikipedia. We currently download new content on a nightly basis.
Does Pfam agree with the content of the Wikipedia entry ?
Pfam has chosen to link families to Wikipedia articles. In some case we have created or edited these articles but in many other cases we have not made any direct contribution to the content of the article. The Wikipedia community does monitor edits to try to ensure that (a) the quality of article annotation increases, and (b) vandalism is very quickly dealt with. However, we would like to emphasise that Pfam does not curate the Wikipedia entries and we cannot guarantee the accuracy of the information on the Wikipedia page.
Editing Wikipedia articles
Before you edit for the first time
Wikipedia is a free, online encyclopedia. Although anyone can edit or contribute to an article, Wikipedia has some strong editing guidelines and policies, which promote the Wikipedia standard of style and etiquette. Your edits and contributions are more likely to be accepted (and remain) if they are in accordance with this policy.
You should take a few minutes to view the following pages:
How your contribution will be recorded
Anyone can edit a Wikipedia entry. You can do this either as a new user or you can register with Wikipedia and log on. When you click on the "Edit Wikipedia article" button, your browser will direct you to the edit page for this entry in Wikipedia. If you are a registered user and currently logged in, your changes will be recorded under your Wikipedia user name. However, if you are not a registered user or are not logged on, your changes will be logged under your computer's IP address. This has two main implications. Firstly, as a registered Wikipedia user your edits are more likely seen as valuable contribution (although all edits are open to community scrutiny regardless). Secondly, if you edit under an IP address you may be sharing this IP address with other users. If your IP address has previously been blocked (due to being flagged as a source of 'vandalism') your edits will also be blocked. You can find more information on this and creating a user account at Wikipedia.
If you have problems editing a particular page, contact us at firstname.lastname@example.org and we will try to help.
The community annotation is a new facility of the Pfam web site. If you have problems editing or experience problems with these pages please contact us.
Methane monooxygenase Edit Wikipedia article
|Particulate methane monooxygenase|
Methane monooxygenase, or MMO, is an enzyme capable of oxidizing the C-H bond in methane as well as other alkanes. Methane monooxygenase belongs to the class of oxidoreductase enzymes (EC 184.108.40.206).
There are two well-studied forms of MMO: the soluble form (sMMO) and the particulate form (pMMO). The active site in sMMO contains a di-iron center bridged by an oxygen atom (Fe-O-Fe), whereas the active site in pMMO utilizes copper, although some propose that pMMO also uses iron. Structures of both proteins have been determined by X-ray crystallography; however, the location and mechanism of the active site in pMMO is still poorly understood and is an area of active research.
The particulate methane monooxygenase and related ammonia monooxygenase are integral membrane proteins, occurring in methanotrophs and ammonia oxidisers, respectively, which are thought to be related. These enzymes have a relatively wide substrate specificity and can catalyse the oxidation of a range of substrates including ammonia, methane, halogenated hydrocarbons, and aromatic molecules. These enzymes are composed of 3 subunits - A (InterPro: IPR003393), B (InterPro: IPR006833) and C (InterPro: IPR006980) - and contain various metal centers, including copper. Particulate methane monooxygenase from Methylococcus capsulatus is an ABC homotrimer, which contains mononuclear and dinuclear copper metal centers, and a third metal center containing a metal ion whose identity in vivo is not certain.
The A subunit from Methylococcus capsulatus (Bath) resides primarily within the membrane and consists of 7 transmembrane helices and a beta-hairpin, which interacts with the soluble region of the B subunit. A conserved glutamate residue is thought to contribute to a metal center.
Methane monooxygenases are found in methanotrophic bacteria, a class of bacteria that exist at the interface of aerobic (oxygen-containing) and anaerobic (oxygen-devoid) environments. One of the more widely studied bacteria of this type is Methylococcus capsulatus (Bath). This bacterium was discovered in the hot springs of Bath, England.
Soluble methane monooxygenase (MMO) systems
Methanotrophic bacteria play an essential role of cycling carbon through anaerobic sediments. The chemistry behind the cycling takes a chemically inert hydrocarbon, methane, and converts it to a more active species, methanol. Other hydrocarbons are oxidized by MMOs, so a new hydroxylation catalyst based on the understanding of MMO systems could possibly make a more efficient use of the world supply of natural gas.
This is a classic monooxygenase reaction in which two reducing equivalents from NAD(P)H are utilized to split the O-O bond of O2. One atom is reduced to water by a 2 e- reduction and the second is incorporated into the substrate to yield methanol:
CH4 + O2 + NAD(P)H + H+ -> CH3OH + NAD(P)+ + H2O
Two forms of MMO have been found: soluble and particulate. The best characterized forms of soluble MMO contains three protein components: hydroxylase, the β unit, and the reductase. Each of which is necessary for effective substrate hydroxylation and NADH oxidation.
X-ray crystallography of the MMO shows that it is a dimer formed of three subunits, α2β2γ2. With 2.2 A resolution, the crystallography shows that MMO is a relatively flat molecule with the dimensions of 60 x 100 x 120 A. In addition, there is a wide canyon running along the dimer interface with an opening in the center of the molecule. Most of the protomers involves helices from the α and β subunits with no participation from the γ subunit. Also, the interactions with the protomers resembles ribonucleotide reductase R2 protein dimer interaction, resembling a heart. Each iron has a six coordinate octahedral environment. The dinuclear iron centers are positioned in the α subunit. Each iron atoms are also coordinated to a histidine δN atom, Fe 1 to a His 147 and Fe 2 to His 246, Fe 1 is a ligated to a monodentate carboxylate, Glu 114, a semi bridging caboxylate, Glu 144, and a water molecule.
The substrate must bind near the active site in order for the reaction to take place. Near to the iron centers, there are hydrophobic pockets. It is thought that here the methane binds and is held until needed. From the X-ray crystallography, there is no direct path to these packets. However, a slight conformation change in the Phe 188 or The 213 side-chains could allow access. This conformational change could be triggered by the binding of a coupling protein and the activase.
Upon reduction, one of the carboxylate ligands undergoes a “1,2 carboxylate” shift from behind a terminal monodentate ligand to a bridging ligand for the two irons, with the second oxygen coordinated to Fe 2. In the reduced form of MMOHred, the ligand environment for the Fe effectively becomes five coordinated, a form that permits the cluster to activate dioxygen. The two irons are at this point oxidized to FeIV and have changed from low-spin ferromagnetic to high-spin antiferromagnetic.
Proposed catalytic cycle and mechanism
From the MMOHred, the diiron centers react with the O2 to form intermediate P. This intermediate is a peroxide species where the oxygens are bound symmetrically, suggested by spectroscopic studies. However, the structure is not known. Intermediate P then converts to intermediate Q, which was proposed to contain two antiferromagnetically coupled high-spin FeIV centers. This compound Q with its diamond core is critical to the oxidizing species for MMO.
There are two mechanisms suggested for the reaction between compound Q and the alkane: radical and nonradical. The radical mechanism starts with abstraction of the hydrogen atom from the substrate to form QH (the rate determining step), hydroxyl bridged compound Q and the free alkyl radical. The nonradical mechanism implies a concerted pathway, occurring via a four-center transition state and leading to a “hydrido-alkyl-Q” compound. As of 1999, the research suggests that the methane oxidation proceeds via a bound-radical mechanism.
It was suggested that the transition state for the radical mechanism involves a torsion motion of the hydroxyl OH ligand before the methyl radical can add to the bridging hydroxyl ligand to form the alcohol. As the radical approaches, the H atom of the alkane leave the coplanar tricoordinate O environment and bends upward to create a tetrahedral tetracoordinate O environment.
The final step for this reaction is the elimination of the alcohol and the regeneration of the catalysts. There are a few ways in which this can occur. It could be a stepwise mechanism that starts with the elimination of the alcohol and an intermediate Fe-O-Fe core, and the latter can eliminate the water and regenerate the enzyme through a 2e- reduction. On the other hand, it can start with a 2e- reduction process of bridging the O1 atom to give a water molecule, followed by elimination of the alcohol and regeneration of the enzyme. In addition, it is possible that there is a concerted mechanism whereby the elimination of the methanol occurs spontaneously with 2e- reduction of the bridging O1 center and regeneration of the catalyst.
- Sazinsky, Matthew H.; Lippard, Stephen J. (2015). "Chapter 6 Methane Monooxygenase: Functionalizing Methane at Iron and Copper". In Peter M.H. Kroneck and Martha E. Sosa Torres. Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. 15. Springer. pp. 205–256. doi:10.1007/978-3-319-12415-5_6.
- Holmes AJ, Costello A, Lidstrom ME, Murrell JC (1995). "Evidence that particulate methane monooxygenase and ammonia monooxygenase may be evolutionarily related". FEMS Microbiol. Lett. 132 (3): 203–208. doi:10.1111/j.1574-6968.1995.tb07834.x. PMID 7590173.
- Arp DJ, Sayavedra-Soto LA, Hommes NG (2002). "Molecular biology and biochemistry of ammonia oxidation by Nitrosomonas europaea". Arch. Microbiol. 178 (4): 250–255. doi:10.1007/s00203-002-0452-0. PMID 12209257.
- Lieberman RL, Rosenzweig AC (2005). "Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane". Nature. 434 (7030): 177–182. doi:10.1038/nature03311. PMID 15674245.
- Dalton, Howard; Whittenbury, Roger (August 1976). "The acetylene reduction technique as an assay for nitrogenase activity in the methane oxidizing bacterium Methylococcus capsulatus strain bath". Archives of Microbiology. SpringLink. 109 (1): 147–151. doi:10.1007/BF00425127. Retrieved 11 January 2016.
- Rosenzweig AC, Frederick CA, Lippard SJ, Nordlund P (1993). "Crystal structure of bacterial non-haem iron hydroxylase that catalyses the biological oxidation of methane". Nature. 366 (6455): 537–543. doi:10.1038/366537a0. PMID 8255292.
- Basch, Harold; et al. (1999). "Mechanism of the Methane -> Methanol Conversion Reaction Catalyzed by Methane Monoxygenase: A Density Function Study". J. Am. Chem. Soc. 121 (31): 7249–7256. doi:10.1021/ja9906296.
- Nordlund P, Sjöberg BM, Eklund H (1990). "Three-dimensional structure of the free radical protein of ribonucleotide reductase". Nature. 345 (6276): 593–598. doi:10.1038/345593a0. PMID 2190093.
- Nordlund P, Eklund H (1993). "Structure and function of the Escherichia coli ribonucleotide reductase protein R2". J. Mol. Biol. 232 (1): 123–164. doi:10.1006/jmbi.1993.1374. PMID 8331655.
- Liu KE, Valentine AM, Qiu D, Edmondson DE, Appelman EH, Spiro TG, Lippard SJ (1995). "Characterization of a Diiron(III) Peroxide Intermediate in the Reaction Cycle of Methane Monooxygenase Hydroxylase from Methylococcus capsulatus (Bath)". Journal of the American Chemical Society. 117 (17): 4997–4998. doi:10.1021/ja00122a032.
- UMich Orientation of Proteins in Membranes protein/pdbid-1yew
- methane monooxygenase at the US National Library of Medicine Medical Subject Headings (MeSH)
This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.
Ammonia monooxygenase Provide feedback
Ammonia monooxygenase plays a key role in the nitrogen cycle and degrades a wide range of hydrocarbons and halogenated hydrocarbons.
This tab holds annotation information from the InterPro database.
InterPro entry IPR003393
Ammonia monooxygenase and the particulate methane monooxygenase are both integral membrane proteins, occurring in ammonia oxidisers and methanotrophs respectively, which are thought to be evolutionarily related [PUBMED:7590173]. These enzymes have a relatively wide substrate specificity and can catalyse the oxidation of a range of substrates including ammonia, methane, halogenated hydrocarbons and aromatic molecules [PUBMED:12209257]. These enzymes are composed of 3 subunits - A (INTERPRO), B (INTERPRO) and C (INTERPRO) - and contain various metal centres, including copper. Particulate methane monooxygenase from Methylococcus capsulatus str. Bath is an ABC homotrimer, which contains mononuclear and dinuclear copper metal centres, and a third metal centre containing a metal ion whose identity in vivo is not certain[PUBMED:15674245].
The A subunit from Methylococcus capsulatus str. Bath resides primarily within the membrane and consists of 7 transmembrane helices and a beta-hairpin which interacts with the soluble region of the B subunit. A conserved glutamate residue is thought to contribute to a metal centre [PUBMED:15674245].
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
The graphic that is shown by default represents the longest sequence with a given architecture. Each row contains the following information:
- the number of sequences which exhibit this architecture
a textual description of the architecture, e.g. Gla, EGF x 2, Trypsin.
This example describes an architecture with one
Gladomain, followed by two consecutive
EGFdomains, and finally a single
- a link to the page in the Pfam site showing information about the sequence that the graphic describes
- the UniProt description of the protein sequence
- the number of residues in the sequence
- the Pfam graphic itself.
Note that you can see the family page for a particular domain by clicking on the graphic. You can also choose to see all sequences which have a given architecture by clicking on the Show link in each row.
Finally, because some families can be found in a very large number of architectures, we load only the first fifty architectures by default. If you want to see more architectures, click the button at the bottom of the page to load the next set.
Loading domain graphics...
We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...
There are various ways to view or download the sequence alignments that we store. We provide several sequence viewers and a plain-text Stockholm-format file for download.
We make a range of alignments for each Pfam-A family:
- the curated alignment from which the HMM for the family is built
- the alignment generated by searching the sequence database using the HMM
- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the UniProtKB sequence database using the family HMM
- alignment generated by searching the NCBI sequence database using the family HMM
- alignment generated by searching the metagenomics sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
- a Java applet developed at the University of Dundee. You will need Java installed before running jalview
- an HTML page showing the whole alignment.Please note: full Pfam alignments can be very large. These HTML views are extremely large and often cause problems for browsers. Please use either jalview or the Pfam viewer if you have trouble viewing the HTML version
- an HTML-based representation of the alignment, coloured according to the posterior-probability (PP) values from the HMM. As for the standard HTML view, heatmap alignments can also be very large and slow to render.
You can download (or view in your browser) a text representation of a Pfam alignment in various formats:
You can also change the order in which sequences are listed in the alignment, change how insertions are represented, alter the characters that are used to represent gaps in sequences and, finally, choose whether to download the alignment or to view it in your browser directly.
You may find that large alignments cause problems for the viewers and the reformatting tool, so we also provide all alignments in Stockholm format. You can download either the plain text alignment, or a gzipped version of it.
We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
Format an alignment
We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...
If you find these logos useful in your own work, please consider citing the following article:
This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.
Note: You can also download the data file for the tree.
Curation and family details
This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.
|Seed source:||Pfam-B_2301 (release 5.4)|
|Number in seed:||10|
|Number in full:||43|
|Average length of the domain:||237.50 aa|
|Average identity of full alignment:||51 %|
|Average coverage of the sequence by the domain:||93.15 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||15|
|Download:||download the raw HMM for this family|
Weight segments by...
Change the size of the sunburst
selected sequences to HMM
a FASTA-format file
- 0 sequences
- 0 species
This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the More....
This chart is a modified "sunburst" visualisation of the species tree for this family. It shows each node in the tree as a separate arc, arranged radially with the superkingdoms at the centre and the species arrayed around the outermost ring.
How the sunburst is generated
The tree is built by considering the taxonomic lineage of each sequence that has a match to this family. For each node in the resulting tree, we draw an arc in the sunburst. The radius of the arc, its distance from the root node at the centre of the sunburst, shows the taxonomic level ("superkingdom", "kingdom", etc). The length of the arc represents either the number of sequences represented at a given level, or the number of species that are found beneath the node in the tree. The weighting scheme can be changed using the sunburst controls.
In order to reduce the complexity of the representation, we reduce the number of taxonomic levels that we show. We consider only the following eight major taxonomic levels:
Colouring and labels
Segments of the tree are coloured approximately according to their superkingdom. For example, archeal branches are coloured with shades of orange, eukaryotes in shades of purple, etc. The colour assignments are shown under the sunburst controls. Where space allows, the name of the taxonomic level will be written on the arc itself.
As you move your mouse across the sunburst, the current node will be highlighted. In the top section of the controls panel we show a summary of the lineage of the currently highlighed node. If you pause over an arc, a tooltip will be shown, giving the name of the taxonomic level in the title and a summary of the number of sequences and species below that node in the tree.
Anomalies in the taxonomy tree
There are some situations that the sunburst tree cannot easily handle and for which we have work-arounds in place.
Missing taxonomic levels
Some species in the taxonomic tree may not have one or more of the main eight levels that we display. For example, Bos taurus is not assigned an order in the NCBI taxonomic tree. In such cases we mark the omitted level with, for example, "No order", in both the tooltip and the lineage summary.
Unmapped species names
The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.
So that these nodes are not simply omitted from the sunburst tree, we group them together in a separate branch (or segment of the sunburst tree). Since we cannot determine the lineage for these unmapped species, we show all levels between the superkingdom and the species as "uncategorised".
Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.
Too many species/sequences
For large species trees, you may see blank regions in the outer layers of the sunburst. These occur when there are large numbers of arcs to be drawn in a small space. If an arc is less than approximately one pixel wide, it will not be drawn and the space will be left blank. You may still be able to get some information about the species in that region by moving your mouse across the area, but since each arc will be very small, it will be difficult to accurately locate a particular species.
The tree shows the occurrence of this domain across different species. More...
We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.
Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.
If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.
For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.
We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.
Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.
We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.
You can use the tree controls to manipulate how the interactive tree is displayed:
- show/hide the summary boxes
- highlight species that are represented in the seed alignment
- expand/collapse the tree or expand it to a given depth
- select a sub-tree or a set of species within the tree and view them graphically or as an alignment
- save a plain text representation of the tree
Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.
There are 5 interactions for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the AMO domain has been found. There are 12 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
Loading structure mapping...