Summary: Alpha adaptin AP2, C-terminal domain

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Alpha adaptin AP2, C-terminal domain

Alpha adaptin is a hetero tetramer which regulates clathrin-bud formation. The carboxyl-terminal appendage of the alpha subunit regulates translocation of endocytic accessory proteins to the bud site.

Literature references

Traub LM, Downs MA, Westrich JL, Fremont DH; , Proc Natl Acad Sci U S A 1999;96:8907-8912.: Crystal structure of the alpha appendage of AP-2 reveals a recruitment platform for clathrin-coat assembly PUBMED:10430869

Internal database links

Similarity to PfamA using HHSearch:

Gamma-COP

External database links

PANDIT:	PF02296
Pseudofam:	PF02296
SCOP:	1qtp
SYSTERS:	Alpha_adaptin_C

This tab holds annotation information from the InterPro database.

InterPro entry IPR003164

Proteins synthesized on the ribosome and processed in the endoplasmic reticulum are transported from the Golgi apparatus to the trans-Golgi network (TGN), and from there via small carrier vesicles to their final destination compartment. These vesicles have specific coat proteins (such as clathrin or coatomer) that are important for cargo selection and direction of transport [PUBMED:15261670]. Clathrin coats contain both clathrin (acts as a scaffold) and adaptor complexes that link clathrin to receptors in coated vesicles. Clathrin-associated protein complexes are believed to interact with the cytoplasmic tails of membrane proteins, leading to their selection and concentration. The two major types of clathrin adaptor complexes are the heterotetrameric adaptor protein (AP) complexes, and the monomeric GGA (Golgi-localising, Gamma-adaptin ear domain homology, ARF-binding proteins) adaptors [PUBMED:17449236, PUBMED:11598180].

AP (adaptor protein) complexes are found in coated vesicles and clathrin-coated pits. AP complexes connect cargo proteins and lipids to clathrin at vesicle budding sites, as well as binding accessory proteins that regulate coat assembly and disassembly (such as AP180, epsins and auxilin). There are different AP complexes in mammals. AP1 is responsible for the transport of lysosomal hydrolases between the TGN and endosomes [PUBMED:15107467]. AP2 associates with the plasma membrane and is responsible for endocytosis [PUBMED:12952931]. AP3 is responsible for protein trafficking to lysosomes and other related organelles [PUBMED:16542748]. AP4 is less well characterised. AP complexes are heterotetramers composed of two large subunits (adaptins), a medium subunit (mu) and a small subunit (sigma). For example, in AP1 these subunits are gamma-1-adaptin, beta-1-adaptin, mu-1 and sigma-1, while in AP2 they are alpha-adaptin, beta-2-adaptin, mu-2 and sigma-2. Each subunit has a specific function. Adaptins recognise and bind to clathrin through their hinge region (clathrin box), and recruit accessory proteins that modulate AP function through their C-terminal ear (appendage) domains. Mu recognises tyrosine-based sorting signals within the cytoplasmic domains of transmembrane cargo proteins [PUBMED:11080148]. One function of clathrin and AP2 complex-mediated endocytosis is to regulate the number of GABA(A) receptors available at the cell surface [PUBMED:17254016].

AP adaptor alpha-adaptin can be divided into a trunk domain and the C-terminal appendage domain (or ear domain), separated by a linker region. The C-terminal appendage domain regulates translocation of endocytic accessory proteins to the bud site [PUBMED:12057195].

This entry represents a subdomain of the appendage (ear) domain of alpha-adaptin from AP clathrin adaptor complexes. This domain has a three-layer arrangement, alpha-beta-alpha, with a bifurcated antiparallel beta-sheet [PUBMED:10430869].

More information about these proteins can be found at Protein of the Month: Clathrin [PUBMED:].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Cellular component	clathrin adaptor complex (GO:0030131)
Biological process	intracellular protein transport (GO:0006886)
Biological process	vesicle-mediated transport (GO:0016192)

Domain organisation

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Alignments

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Alignment:	Seed (22) Full (206) NCBI (260) Metagenomics (4)
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Alignment:	Seed (22) Full (206)
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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 (22) Full (206) NCBI (260) Metagenomics (4)
Full length sequences	Full-sequences (206)

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.

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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

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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:

Pfam-B_8859 (release 5.2)

Previous IDs:

none

Type:

Family

Author:

Mian N, Bateman A, Griffiths-Jones SR

Number in seed:

22

Number in full:

206

Average length of the domain:

110.20 aa

Average identity of full alignment:

36 %

Average coverage of the sequence by the domain:

12.24 %

HMM information

HMM build commands:

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

search method: hmmsearch -Z 15929002 -E 1000 --cpu 4 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	24.2	24.2
Trusted cut-off	24.6	24.2
Noise cut-off	23.6	23.9

Model length:

113

Family (HMM) version:

11

Download:

download the raw HMM for this family

Species distribution

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Archea	Eukaryota
Bacteria	Other sequences
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Viroids	Unclassified sequence

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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.

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Interactions

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Alpha_adaptinC2

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 Alpha_adaptin_C domain has been found. There are 9 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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Family: Alpha_adaptin_C (PF02296)

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