Summary: Staphylococcal nuclease homologue
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This is the Wikipedia entry entitled "Micrococcal nuclease". More...
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Micrococcal nuclease Edit Wikipedia article
Micrococcal Nuclease (S7 Nuclease) is a relatively nonspecific endo-exonuclease that digests single-stranded and double-stranded nucleic acids, but is more active on single-stranded substrates. Cleavage of DNA or RNA occurs preferentially at AT or AU-rich regions yielding mononucleotides and oligonucleotides with terminal 3'-phosphates. The enzyme activity is strictly dependent on Ca2+.
Source E.coli cells carrying a cloned nuc gene encoding Staphylococcus aureus extracellular nuclease (micrococcal nuclease).
Applications Hydrolysis of nucleic acids in crude cell-free extracts. Sequencing of RNA . Studies of chromatin structure. A model for protein folding and for structure-function studies
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.
Staphylococcal nuclease homologue Provide feedback
Present in all three domains of cellular life. Four copies in the transcriptional coactivator p100: these, however, appear to lack the active site residues of Staphylococcal nuclease. Positions 14 (Asp-21), 34 (Arg-35), 39 (Asp-40), 42 (Glu-43) and 110 (Arg-87) [SNase numbering in parentheses] are thought to be involved in substrate-binding and catalysis.
Callebaut I, Mornon JP; , Biochem J 1997;321:125-132.: The human EBNA-2 coactivator p100: multidomain organization and relationship to the staphylococcal nuclease fold and to the tudor protein involved in Drosophila melanogaster development. PUBMED:9003410 EPMC:9003410
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR016071
Staphylococcus aureus nuclease (SNase) homologues, previously thought to be restricted to bacteria and archaea, are also in eukaryotes. Staphylococcal nuclease has a multi-domain organisation [ PUBMED:9003410 ]. The human cellular coactivator p100 contains four repeats, each of which is a SNase homologue. These repeats are unlikely to possess SNase-like activities as each lacks equivalent SNase catalytic residues, yet they may mediate p100's single-stranded DNA-binding function [ PUBMED:9041650 ]. A variety of proteins including many that are still uncharacterised belong to this group.
SNase domains have an OB-fold consisting of a closed or partly open beta-barrel with Greek key topology [ PUBMED:8475069 ].
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
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This clan covers the Tudor domain 'royal family' . This includes chromo, MBT, PWWP and tudor domains. The chromo domain is a comprised of approximately 50 amino acid residues. There are usually one to three Chromo domains found in a single protein. In some chromo domain containing proteins, a second related chromo domain has been found and is referred to as the Chromo-shadow domain. The structure of the Chromo and Chromo-shadow domains reveal an OB-fold, a fold found in a variety of prokaryotic and eukaryotic nucleic acid binding proteins. More specifically,the chromo-domain structure reveals a three beta strands that are packed against an alpha helix. Interestingly, a similar structure is found in the archaeal chromatin proteins (7kDa DNA-binding domain). These are sequence neutral DNA binding proteins. The DNA binding in these archaeal proteins is mediated through the triple stranded beta sheet. These archaeal domains are though to represent an ancestral chromo domain. Homologs of the chromo domain have been found in fission yeast, ciliated protozoa and all animal species, but appear to be absent in eubacteria, budding yeast and plants . The precise function of the chromo domain is unclear, but the chromo domain is thought to act as a targeting module for chromosomal proteins, although the chromosomal contexts and functional contexts being targeted vary. In all cases studies, the chromo domains are found in proteins that are involved in transcription regulation, positive and negative .
The clan contains the following 33 members:53-BP1_Tudor 7kD_DNA_binding Agenet Chromo Chromo_2 Chromo_shadow Cul7 DUF1325 DUF4537 DUF4819 GEN1_C Hva1_TUDOR LBR_tudor LytTR MBT Mtf2_C ProQ_C PWWP Rad9_Rad53_bind RBB1NT SAWADEE SMN SNase TTD TUDOR Tudor-knot Tudor_1_RapA Tudor_2 Tudor_3 Tudor_4 Tudor_5 Tudor_FRX1 Tudor_RapA
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 and the UniProtKB 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
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- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the UniProtKB sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
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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.
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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:||Alignment kindly provided by SMART|
|Number in seed:||18|
|Number in full:||14812|
|Average length of the domain:||107.7 aa|
|Average identity of full alignment:||22 %|
|Average coverage of the sequence by the domain:||45.09 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||20|
|Download:||download the raw HMM for this family|
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a FASTA-format file
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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:
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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.
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 SNase domain has been found. There are 349 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 sequence.
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AlphaFold Structure Predictions
The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.