Summary

SAM domain (Sterile alpha motif)

It has been suggested that SAM is an evolutionarily conserved protein binding domain that is involved in the regulation of numerous developmental processes in diverse eukaryotes. The SAM domain can potentially function as a protein interaction module through its ability to homo- and heterooligomerise with other SAM domains.

Literature references

Ponting CP; , Protein Sci 1995;4:1928-1930.: SAM: a novel motif in yeast sterile and Drosophila polyhomeotic proteins. PUBMED:8528090
Schultz J, Ponting CP, Hofmann K, Bork P; , Protein Sci 1997;6:249-253.: SAM as a protein interaction domain involved in developmental regulation. PUBMED:9007998
Stapleton D, Balan I, Pawson T, Sicheri F; , Nat Struct Biol 1999;6:44-49.: The crystal structure of an Eph receptor SAM domain reveals a mechanism for modular dimerization. PUBMED:9886291

InterPro entry IPR001660

The sterile alpha motif (SAM) domain is a putative protein interaction module present in a wide variety of proteins PUBMED:9007998 involved in many biological processes. The SAM domain that spreads over around 70 residues is found in diverse eukaryotic organisms PUBMED:9886291. SAM domains have been shown to homo- and hetero-oligomerise, forming multiple self-association architectures and also binding to various non-SAM domain-containing proteins PUBMED:9343432, nevertheless with a low affinity constant PUBMED:9933164. SAM domains also appear to possess the ability to bind RNA PUBMED:14659692. Smaug, a protein that helps to establish a morphogen gradient in Drosophila embryos by repressing the translation of nanos (nos) mRNA, binds to the 3' untranslated region (UTR) of nos mRNA via two similar hairpin structures. The 3D crystal structure of the Smaug RNA-binding region shows a cluster of positively charged residues on the Smaug-SAM domain, which could be the RNA-binding surface. This electropositive potential is unique among all previously determined SAM-domain structures and is conserved among Smaug-SAM homologs. These results suggest that the SAM domain might have a primary role in RNA binding.

Structural analyses show that the SAM domain is arranged in a small five-helix bundle with two large interfaces PUBMED:9343432. In the case of the SAM domain of EphB2, each of these interfaces is able to form dimers. The presence of these two distinct intermonomers binding surface suggest that SAM could form extended polymeric structures PUBMED:9933164.

Clan

This family is a member of clan SAM (CL0003), which contains the following 4 members:

SAM_1 SAM_2 SAM_PNT Ste50p-SAM

External database links

HOMSTRAD:	SAM
PANDIT:	PF00536
SCOP:	1b0x
SMART:	SAM
SYSTERS:	SAM_1

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 (67) Full (1691) NCBI (4061) Metagenomics (102)
Viewer:

Formatting options

Alignment:	Seed (67) Full (1691)
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 (67) Full (1691) NCBI (4061) Metagenomics (102)
Full length sequences	Full-sequences (1691)

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:

[1],[2]

Previous IDs:

SAM_1;

Type:

Domain

Author:

Bateman A

Number in seed:

67

Number in full:

1691

Average length of the domain:

62.80 aa

Average identity of full alignment:

22 %

Average coverage of the sequence by the domain:

8.05 %

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	20.7	20.7
Trusted cut-off	20.7	20.7
Noise cut-off	20.6	20.6

Model length:

64

Family (HMM) version:

23

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 are 2 interactions for this family. More...

SAM_1 SAM_2

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 MSD 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 SAM_1 domain has been found.

Loading structure mapping...

Family: SAM_1 (PF00536)

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