Summary: Signal peptidase, peptidase S26
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 "Signal peptidase". More...
Signal peptidase Edit Wikipedia article
Initially observed in preparations of Endoplasmci reticulum (ER)-derived membranes, so called "microsomes" from mouse myeloma cells [1], 'signal peptidase convert secretory and some membrane proteins to their mature form. The key observation by Milstein et al. was that immunoglobulin light chains were produced in a higher molecular weight form, which became processed by the microsomal fraction. This finding was directly followed by the discovery of the ER translocation machinery [2]. Signal peptidases are also found in prokaryotes as well as the protein import machinery of mitochondria and chloroplasts [3].
All signal peptidases described so far are serine proteases. The active site that endoproteolytically cleaves signal peptides from translocated precursor proteins is located at the extracytoplasmic site of the membrane. The eukaryotic signal peptidase is an integral membrane protein complex. The first subunit, which was identified genetically, is Sec11, yeast membrane protein of 17 kDa. Sec11 is associated with three subunits termed Spc3p (21 kDa), Spc2p (18 kDa) and Spc1p (11 kDa). Sec11 is the only essential factor for signal peptide processing as can be deduced from a growth defect upon its deletion [4]. The functional signal peptidase complex was first purified from canine microsomes [5]. The five mammalian subunits are named SPC12, SPC18, SPC21, SPC22/23 and SPC25 according to their molecular weight.
- ^ Milstein, C., Brownlee, G. G., Harrison, T. M., and Mathews, M. B. (1972). A possible precursor of immunoglobulin light chains. Nat New Biol 239, PP. 117-120
- ^ Blobel, G., and Dobberstein, B. (1975). Transfer of proteins across membranes. I. Presence of proteolytically processed and unprocessed nascent immunoglobulin light chains on membrane-bound ribosomes of murine myeloma. J Cell Biol 67, PP. 835-851
- ^ Paetzel, M., Karla, A., Strynadka, N. C., and Dalbey, R. E. (2002b). Signal peptidases. Chem Rev 102, PP. 4549-4580
- ^ Bohni, P. C., Deshaies, R. J., and Schekman, R. W. (1988). SEC11 is required for signal peptide processing and yeast cell growth. J Cell Biol 106, PP. 1035-1042
- ^ Evans, E. A., Gilmore, R., and Blobel, G. (1986). Purification of microsomal signal peptidase as a complex. Proc Natl Acad Sci U S A 83, PP. 581-585
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.
Signal peptidase, peptidase S26 Provide feedback
This is a family of membrane signal serine endopeptidases which function in the processing of newly-synthesised secreted proteins. Peptidase S26 removes the hydrophobic, N-terminal, signal peptides as proteins are translocated across membranes. The active site residues take the form of a catalytic dyad that is Ser, Lys in subfamily S26A; the Ser is the nucleophile in catalysis, and the Lys is the general base.
Internal database links
SCOOP: | Peptidase_S24 |
Similarity to PfamA using HHSearch: | Peptidase_S24 |
External database links
MEROPS: | S26 |
This tab holds annotation information from the InterPro database.
InterPro entry IPR019533
This entry represents a domain found in some members of the S26A family of serine endopeptidases. Peptidases S26A (signal peptidase I) removes the hydrophobic, N-terminal signal peptides as proteins are translocated across membranes. The type I signal peptidases are unique serine proteases that utilize a serine/lysine catalytic dyad mechanism in place of the classical serine/histidine/aspartic acid catalytic triad mechanism [ PUBMED:15546672 ]. Peptidases S26B includes eukaryotic microsomal signal peptidases involved in the removal of signal peptides from secretory proteins as they pass into the endoplasmic reticulum lumen [ PUBMED:7845208 ]. Peptidases 26C (TraF signal peptidase) are found in operons that encode elements of conjugative transfer systems.
Gene Ontology
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
Molecular function | serine-type endopeptidase activity (GO:0004252) |
Biological process | signal peptide processing (GO:0006465) |
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 Peptidase_SF (CL0299), which has the following description:
This clan includes the peptidase S24 and S26 families. These families adopt a mainly beta fold. Members of the family S24 have an additional C-terminal domain containing a bundle of three helices presumably important for binding DNA.
The clan contains the following 3 members:
Peptidase_S24 Peptidase_S26 Phage_CI_CAlignments
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...
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.
Seed (71) |
Full (23661) |
Representative proteomes | UniProt (95907) |
||||
---|---|---|---|---|---|---|---|
RP15 (3463) |
RP35 (11578) |
RP55 (23213) |
RP75 (38157) |
||||
Jalview | |||||||
HTML | |||||||
PP/heatmap | 1 |
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key:
available,
not generated,
— not available.
Format an alignment
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.
Seed (71) |
Full (23661) |
Representative proteomes | UniProt (95907) |
||||
---|---|---|---|---|---|---|---|
RP15 (3463) |
RP35 (11578) |
RP55 (23213) |
RP75 (38157) |
||||
Raw Stockholm | |||||||
Gzipped |
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
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'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
Seed source: | Manual |
Previous IDs: | none |
Type: | Domain |
Sequence Ontology: | SO:0000417 |
Author: |
Mistry J |
Number in seed: | 71 |
Number in full: | 23661 |
Average length of the domain: | 152.6 aa |
Average identity of full alignment: | 23 % |
Average coverage of the sequence by the domain: | 71.63 % |
HMM information
HMM build commands: |
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
|
||||||||||||
Model details: |
|
||||||||||||
Model length: | 170 | ||||||||||||
Family (HMM) version: | 12 | ||||||||||||
Download: | download the raw HMM for this family |
Species distribution
Sunburst controls
HideWeight segments by...
Change the size of the sunburst
Colour assignments
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
Selections
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...
Tree controls
HideThe tree shows the occurrence of this domain across different species. More...
Loading...
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.
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 Peptidase_S26 domain has been found. There are 25 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.
Loading structure mapping...
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.