Summary

Sir2 family

This region is characteristic of Silent information regulator 2 (Sir2) proteins, or sirtuins. These are protein deacetylases that depend on nicotine adenine dinucleotide (NAD). They are found in many subcellular locations, including the nucleus, cytoplasm and mitochondria. Eukaryotic forms play in important role in the regulation of transcriptional repression. Moreover, they are involved in microtubule organisation and DNA damage repair processes [1].

Literature references

North BJ, Verdin E; , Genome Biol 2004;5:224.: Sirtuins: Sir2-related NAD-dependent protein deacetylases. PUBMED:15128440

InterPro entry IPR003000

These sequences represent the Sir2 family of NAD+-dependent deacetylases. Silent Information Regulator protein of Saccharomyces cerevisiae (Sir2p) is one of several factors critical for silencing at least three loci. Among them, it is unique because it silences the rDNA as well as the mating type loci and telomeres. Sir2p interacts in a complex with itself and with Sir3p and Sir4p, two proteins that are able to interact with nucleosomes. In addition Sir2p also interacts with ubiquitination factors and/or complexes PUBMED:9214640. Unlike Sir3p and Sir4p, for which no homologues are known, Sir2p is part of a multigene family in yeast, the homolgues being HST1, HST2, HST3 and HST4. Highly conserved structural homologues also occur in other organisms ranging from bacteria to man and plants. Proteins of this family have been proposed to play a role in silencing, chromosome stability and ageingPUBMED:7498786. In addition, an in vitro ADP ribosyltransferase activity has been associated with Escherichia coli and human members of this family PUBMED:10381378. Homologues of Sir2 share a core domain including the GAG and NID motifs and a putative C4 Zinc finger. The regions containing these three conserved motifs are individually essential for Sir2 silencing function, as are the four cysteins PUBMED:10473645. In addition, the conserved residues HG next to the putative Zn finger have been shown to be essential for the ADP ribosyltransferase activity PUBMED:10381378. Sir2-like enzymes catalyze a reaction in which the cleavage of NAD(+)and histone and/or protein deacetylation are coupled to the formation of O-acetyl-ADP-ribose, a novel metabolite. The dependence of the reaction on both NAD(+) and the generation of this potential second messenger offers new clues to understanding the function and regulation of nuclear, cytoplasmic and mitochondrial Sir2-like enzymes PUBMED:12517451.

Clan

This family is a member of clan FAD_DHS (CL0085), which contains the following 6 members:

CO_dh DS ETF_alpha PNTB SIR2 TPP_enzyme_M

Gene Ontology

Molecular function	NAD binding (GO:0070403)
	hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds, in linear amides (GO:0016811)
	zinc ion binding (GO:0008270)
Biological process	chromatin silencing (GO:0006342)
	regulation of transcription (GO:0045449)
	protein amino acid deacetylation (GO:0006476)

External database links

PANDIT:	PF02146
PROSITE profile:	PS50305
SCOP:	1j8f
SYSTERS:	SIR2

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Alignments

There are various ways to view or download the sequence alignments that we store. You can use a sequence viewer to look at either the seed or full alignment for the family, or you can look at a plain text version of the sequence in a variety of different formats. More...

View options

Alignment:	Seed (21) Full (2130) NCBI (2674) Metagenomics (910)
Viewer:

Formatting options

Alignment:	Seed (21) Full (2130)
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

Very large alignments can often cause problems for the formatting tool above. If you find that downloading or viewing a large alignment is problematic, you can also download a gzip-compressed, Stockholm-format file containing the seed or full alignment for this family.

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

The main seed and full alignments are generated using sequences from the UniProt sequence database. However, we also generate alignments using sequences from the NCBI sequence database and the "metaseq" metagenomics dataset.

You can view alignments from these two additional datasets using the form above, or you can download alignments of NCBI or metagenomics sequences, as gzip-compressed files.

Pfam alignments:	Seed (21) Full (2130) NCBI (2674) Metagenomics (910)
Full length sequences	Full-sequences (2130)

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER2.

HMM logo

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...

Trees

This page displays the phylogenetic tree for this family. 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 or full alignments.

Note: You can also download the data files for the seed, full, NCBI or metagenomics trees.

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.

Curation

Seed source:

IPR003000

Previous IDs:

none

Type:

Family

Author:

Mian N, Bateman A

Number in seed:

21

Number in full:

2130

Average length of the domain:

177.90 aa

Average identity of full alignment:

30 %

Average coverage of the sequence by the domain:

54.13 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 9421015 -E 1000 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	20.6	20.6
Trusted cut-off	20.7	20.6
Noise cut-off	20.0	20.5

Model length:

181

Family (HMM) version:

10

Download:

download the raw HMM for this family

Species distribution

Tree controls

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The tree shows the occurrence of this domain across different species. More...

Species trees

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.

Interactive tree

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

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Interactions

There is 1 interaction for this family. More...

SIR2

Structures

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 SIR2 domain has been found.

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Family: SIR2 (PF02146)

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