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Ribonuclease Edit Wikipedia article
Ustilago sphaerogena Ribonuclease U2 with AMP PDB entry 
Ribonuclease (commonly abbreviated RNase) is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 (for the phosphorolytic enzymes) and 3.1 (for the hydrolytic enzymes) classes of enzymes.
All organisms studied contain many RNases of many different classes, showing that RNA degradation is a very ancient and important process. As well as cleaning of cellular RNA that is no longer required, RNases play key roles in the maturation of all RNA molecules, both messenger RNAs that carry genetic material for making proteins, and non-coding RNAs that function in varied cellular processes. In addition, active RNA degradation systems are a first defense against RNA viruses, and provide the underlying machinery for more advanced cellular immune strategies such as RNAi.
Some cells also secrete copious quantities of non-specific RNases such as A and T1. RNases are, therefore, extremely common, resulting in very short lifespans for any RNA that is not in a protected environment. It is worth noting that all intracellular RNAs are protected from RNase activity by a number of strategies including 5' end capping, 3' end polyadenylation, and folding within an RNA protein complex (ribonucleoprotein particle or RNP).
Another mechanism of protection is ribonuclease inhibitor (RI), which comprises a relatively large fraction of cellular protein (~0.1%) in some cell types, and which binds to certain ribonucleases with the highest affinity of any protein-protein interaction; the dissociation constant for the RI-RNase A complex is ~20 fM under physiological conditions. RI is used in most laboratories that study RNA to protect their samples against degradation from environmental RNases.
Similar to restriction enzymes, which cleave highly specific sequences of double-stranded DNA, a variety of endoribonucleases that recognize and cleave specific sequences of single-stranded RNA have been recently classified.
RNases play a critical role in many biological processes, including angiogenesis and self-incompatibility in flowering plants (angiosperms). Also, RNases in prokaryotic toxin-antitoxin systems are proposed to function as plasmid stability loci, and as stress-response elements when present on the chromosome
Major types of endoribonucleases
- EC 188.8.131.52: RNase A is an RNase that is commonly used in research. RNase A (e.g., bovine pancreatic ribonuclease A: ) is one of the hardiest enzymes in common laboratory usage; one method of isolating it is to boil a crude cellular extract until all enzymes other than RNase A are denatured. It is specific for single-stranded RNAs. It cleaves the 3'-end of unpaired C and U residues, ultimately forming a 3'-phosphorylated product via a 2',3'-cyclic monophosphate intermediate. It does not require any cofactors for its activity 
- EC 184.108.40.206: RNase H is a ribonuclease that cleaves the RNA in a DNA/RNA duplex to produce ssDNA. RNase H is a non-specific endonuclease and catalyzes the cleavage of RNA via a hydrolytic mechanism, aided by an enzyme-bound divalent metal ion. RNase H leaves a 5'-phosphorylated product.
- EC 220.127.116.11: RNase III is a type of ribonuclease that cleaves rRNA (16s rRNA and 23s rRNA) from transcribed polycistronic RNA operon in prokaryotes. It also digests double strands RNA (dsRNS)-Dicer family of RNAse, cutting pre-miRNA (60–70bp long) at a specific site and transforming it in miRNA (22–30bp), that is actively involved in the regulation of transcription and mRNA life-time.
- EC number 3.1.26.-??: RNase L is an interferon-induced nuclease that, upon activation, destroys all RNA within the cell
- EC 18.104.22.168: RNase P is a type of ribonuclease that is unique in that it is a ribozyme – a ribonucleic acid that acts as a catalyst in the same way as an enzyme. Its function is to cleave off an extra, or precursor, sequence on tRNA molecules. RNase P is one of two known multiple turnover ribozymes in nature (the other being the ribosome). A form of RNase P that is a protein and does not contain RNA has recently been discovered.
- EC number 3.1.??: RNase PhyM is sequence specific for single-stranded RNAs. It cleaves 3'-end of unpaired A and U residues.
- EC 22.214.171.124: RNase T1 is sequence specific for single-stranded RNAs. It cleaves 3'-end of unpaired G residues.
- EC 126.96.36.199: RNase T2 is sequence specific for single-stranded RNAs. It cleaves 3'-end of all 4 residues, but preferentially 3'-end of As.
- EC 188.8.131.52: RNase U2 is sequence specific for single-stranded RNAs. It cleaves 3'-end of unpaired A residues.
- EC 184.108.40.206: RNase V is specific for polyadenine and polyuridine RNA.
Major types of exoribonucleases
- EC number EC 220.127.116.11: Polynucleotide Phosphorylase (PNPase) functions as an exonuclease as well as a nucleotidyltransferase.
- EC number EC 18.104.22.168: RNase PH functions as an exonuclease as well as a nucleotidyltransferase.
- EC number 3.1.??: RNase R is a close homolog of RNase II, but it can, unlike RNase II, degrade RNA with secondary structures without help of accessory factors.
- EC number EC 22.214.171.124: RNase D is involved in the 3'-to-5' processing of pre-tRNAs.
- EC number 3.1.??: RNase T is the major contributor for the 3'-to-5' maturation of many stable RNAs.
- EC 126.96.36.199: Oligoribonuclease degrades short oligonucleotides to mononucleotides.
- EC 188.8.131.52: Exoribonuclease I degrades single-stranded RNA from 5'-to-3', exists only in eukaryotes.
- EC 184.108.40.206: Exoribonuclease II is a close homolog of Exoribonuclease I.
Although, usually most of exo- and endoribonucleases are not sequence specific, recently CRISPR/Cas system natively recognizing and cutting DNA was engineered to cleave ssRNA in sequence specific manner.
RNase contamination during RNA extraction
The extraction of RNA in molecular biology experiments is greatly complicated by the presence of ubiquitous and hardy ribonucleases that degrade RNA samples. Certain RNases can be extremely hardy and inactivating them is difficult compared to neutralizing DNases. In addition to the cellular RNases that are released, there are several RNases that are present in the environment. RNases have evolved to have many extracellular functions in various organisms. For example, RNase 7, a member of the RNase A superfamily, is secreted by human skin and serves as a potent antipathogen defence. In these secreted RNases, the enzymatic RNase activity may not even be necessary for its new, exapted function. For example, immune RNases act by destabilizing the cell membranes of bacteria.
- Cuchillo, C. M.; Nogués, M. V.; Raines, R. T. (2011). "Bovine pancreatic ribonuclease: Fifty years of the first enzymatic reaction mechanism". Biochemistry 50: 7835–7841. doi:10.1021/bi201075b. PMC 3172371. PMID 21838247.
- J. Holzmann, P. Frank, E. Löffler, K. Bennett, C. Gerner & W. Rossmanith (2008). "RNase P without RNA: Identification and functional reconstitution of the human mitochondrial tRNA processing enzyme". Cell 135 (3): 462–474. doi:10.1016/j.cell.2008.09.013. PMID 18984158.
- Tamulaitis, Gintautas; Kazlauskiene, Migle; Manakova, Elena; Venclovas, Česlovas; Nwokeoji, Alison O.; Dickman, Mark J.; Horvath, Philippe; Siksnys, Virginijus (2014). "Programmable RNA Shredding by the Type III-A CRISPR-Cas System of Streptococcus thermophilus". Molecular Cell 56 (4): 506–517. doi:10.1016/j.molcel.2014.09.027. ISSN 1097-2765.
- Rossier, O.; Dao, J.; Cianciotto, N. P. (2009). "A type II secreted RNase of Legionella pneumophila facilitates optimal intracellular infection of Hartmannella vermiformis". Microbiology 155 (3): 882. doi:10.1099/mic.0.023218-0.
- Luhtala, N.; Parker, R. (2010). "T2 Family ribonucleases: Ancient enzymes with diverse roles". Trends in Biochemical Sciences 35 (5): 253. doi:10.1016/j.tibs.2010.02.002.
- Dyer, K. D.; Rosenberg, H. F. (2006). "The RNase a superfamily: Generation of diversity and innate host defense". Molecular Diversity 10 (4): 585. doi:10.1007/s11030-006-9028-2.
- Harder, J. (2002). "RNase 7, a Novel Innate Immune Defense Antimicrobial Protein of Healthy Human Skin". Journal of Biological Chemistry 277 (48): 46779. doi:10.1074/jbc.M207587200.
- Köten, B.; Simanski, M.; Gläser, R.; Podschun, R.; Schröder, J. M.; Harder, J. R. (2009). "RNase 7 Contributes to the Cutaneous Defense against Enterococcus faecium". PLoS ONE 4 (7): e6424. doi:10.1371/journal.pone.0006424.
- Huang, Y. -C.; Lin, Y. -M.; Chang, T. -W.; Wu, S. -J.; Lee, Y. -S.; Chang, M. D. -T.; Chen, C.; Wu, S. -H.; Liao, Y. -D. (2006). "The Flexible and Clustered Lysine Residues of Human Ribonuclease 7 Are Critical for Membrane Permeability and Antimicrobial Activity". Journal of Biological Chemistry 282 (7): 4626. doi:10.1074/jbc.M607321200.
- Rosenberg, H. F. (2008). "RNase a ribonucleases and host defense: An evolving story". Journal of Leukocyte Biology 83 (5): 1079. doi:10.1189/jlb.1107725.
- D'Alessio G and Riordan JF, eds. (1997) Ribonucleases: Structures and Functions, Academic Press.
- Gerdes K, Christensen SK and Lobner-Olesen A (2005). "Prokaryotic toxin-antitoxin stress response loci". Nat. Rev. Microbiol. (3) 371–382.
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.
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This enzyme hydrolyses RNA and oligoribonucleotides.
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR000026
Ribonuclease N1 (RNase N1) is a guanine-specific ribonuclease from fungi. RNase T1 and other bacteria RNases are related.
The enzyme hydrolyses the phosphodiester bonds in RNA and oligoribonucleotides [PUBMED:8110767], resulting in 3'-nucleoside monophosphates via 2',3'-cyclophosphate intermediates.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||endoribonuclease activity (GO:0004521)|
|RNA binding (GO:0003723)|
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:
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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
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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.
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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.
|Number in seed:||160|
|Number in full:||430|
|Average length of the domain:||85.10 aa|
|Average identity of full alignment:||30 %|
|Average coverage of the sequence by the domain:||46.45 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 11927849 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||17|
|Download:||download the raw HMM for this family|
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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.
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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.
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 Ribonuclease domain has been found. There are 344 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.
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