Please note: this site relies heavily on the use of javascript. Without a javascript-enabled browser, this site will not function correctly. Please enable javascript and reload the page, or switch to a different browser.
368  structures 94  species 15  interactions 1488  sequences 25  architectures

Family: S_100 (PF01023)

Summary: S-100/ICaBP type calcium binding domain

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 "S-100 protein". More...

S-100 protein Edit Wikipedia article

Redirect to:

  • This is a redirect from a page that has been moved (renamed). This page was kept as a redirect to avoid breaking links, both internal and external, that may have been made to the old page name. For more information follow the category link.

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

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.

S-100/ICaBP type calcium binding domain Provide feedback

The S-100 domain is a subfamily of the EF-hand calcium binding proteins.

Literature references

  1. Sastry M, Ketchem RR, Crescenzi O, Weber C, Lubienski MJ, Hidaka H, Chazin WJ; , Structure 1998;6:223-231.: The three-dimensional structure of Ca(2+)-bound calcyclin: implications for Ca(2+)-signal transduction by S100 proteins. PUBMED:9519412 EPMC:9519412

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR013787

The calcium-binding domain found in S100 and CaBP-9k proteins is a subfamily of the EF-hand calcium-binding domain [PUBMED:15284904]. S100s are small dimeric acidic calcium and zinc-binding proteins abundant in the brain, with S100B playing an important role in modulating the proliferation and differentiation of neurons and glia cells [PUBMED:15006498]. S100 proteins have two different types of calcium-binding sites: a low affinity one with a special structure, and a 'normal' EF-hand type high-affinity site.

Calbindin-D9k (CaBP-9k) also belong to this family of proteins, but it does not form dimers. CaBP-9k is a cytosolic protein expressed in a variety of tissues. Although its precise function is unknown, it appears to be under the control of the steroid hormones oestrogen and progesterone in the female reproductive system [PUBMED:16288660]. In the intestine, CaBP-9k may be involved in calcium absorption by mediating intracellular diffusion [PUBMED:12520541].

This entry represents a subdomain of the calcium-binding domain found in S100, CaBP-9k, and related proteins.

Domain organisation

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

Loading domain graphics...

Pfam Clan

This family is a member of clan EF_hand (CL0220), which has the following description:

The EF hand is a calcium binding domain found in a wide variety of proteins [1].

The clan contains the following 17 members:

Caleosin Dockerin_1 EF-hand_1 EF-hand_10 EF-hand_11 EF-hand_2 EF-hand_3 EF-hand_4 EF-hand_5 EF-hand_6 EF-hand_7 EF-hand_8 EF-hand_9 EF-hand_like EFhand_Ca_insen S_100 SPARC_Ca_bdg


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 using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics sequence database. More...

View options

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.

Representative proteomes NCBI
Jalview View  View  View  View  View  View  View  View 
HTML View  View  View  View  View  View     
PP/heatmap 1 View  View  View  View  View     
Pfam viewer View  View             

1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

Format an alignment

Representative proteomes NCBI

Download options

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.

Representative proteomes NCBI
Raw Stockholm Download   Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download   Download  

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

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 HMMER3.

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...


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.

Curation View help on the curation process

Seed source: Pfam-B_242 (release 3.0)
Previous IDs: S_100_domain;
Type: Domain
Author: Finn RD, Bateman A
Number in seed: 214
Number in full: 1488
Average length of the domain: 41.90 aa
Average identity of full alignment: 36 %
Average coverage of the sequence by the domain: 15.80 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.3 20.3
Trusted cut-off 20.3 20.6
Noise cut-off 20.2 20.1
Model length: 43
Family (HMM) version: 15
Download: download the raw HMM for this family

Species distribution

Sunburst controls


Weight segments by...

Change the size of the sunburst


Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


Align selected sequences to HMM

Generate a FASTA-format file

Clear selection

This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

Loading sunburst data...

Tree controls


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


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 15 interactions for this family. More...

Ig_2 EF-hand_1 EF-hand_1 IL1 Myosin_tail_1 FGF F-actin_cap_A SGS IL1 Myosin_tail_1 F-actin_cap_A S_100 C2 C2 FGF


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 S_100 domain has been found. There are 368 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...