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Gene Family: Clathrin/coatomer adaptor, adaptin-like, N-terminal domain containing

Also known as : "IPR002553"

Genes contained within the family: 14

Approved Symbol Approved Name Previous Symbols Synonyms Chromosome
AP1B1 adaptor related protein complex 1 subunit beta 1 ADTB1, CLAPB2 BAM22, AP105A 22q12.2
AP1G1 adaptor related protein complex 1 subunit gamma 1 CLAPG1, ADTG 16q22.2
AP1G2 adaptor related protein complex 1 subunit gamma 2 G2AD 14q11.2
AP2A1 adaptor related protein complex 2 subunit alpha 1 CLAPA1, ADTAA 19q13.33
AP2A2 adaptor related protein complex 2 subunit alpha 2 CLAPA2, ADTAB DKFZP564D1864, HYPJ, KIAA0899, HIP9 11p15.5
AP2B1 adaptor related protein complex 2 subunit beta 1 ADTB2, CLAPB1 17q12
AP3B1 adaptor related protein complex 3 subunit beta 1 ADTB3A, HPS2 5q14.1
AP3B2 adaptor related protein complex 3 subunit beta 2 NAPTB 15q25.2
AP3D1 adaptor related protein complex 3 subunit delta 1 ADTD 19p13.3
AP4B1 adaptor related protein complex 4 subunit beta 1 SPG47 BETA-4 1p13.2
AP4E1 adaptor related protein complex 4 subunit epsilon 1 AP-4-EPSILON, SPG51 15q21.2
COPB1 coatomer protein complex subunit beta 1 COPB 11p15.2
COPG1 coatomer protein complex subunit gamma 1 COPG 3q21.3
COPG2 coatomer protein complex subunit gamma 2 2-COP 7q32.2


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. This traffic is bidirectional, to ensure that proteins required to form vesicles are recycled. Vesicles have specific coat proteins (such as clathrin or coatomer) that are important for cargo selection and direction of transfer [PMID: 15261670]. Clathrin coats contain both clathrin 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 [PMID: 17449236]. All AP complexes are heterotetramers composed of two large subunits (adaptins), a medium subunit (mu) and a small subunit (sigma). Each subunit has a specific function. Adaptin subunits recognise and bind to clathrin through their hinge region (clathrin box), and recruit accessory proteins that modulate AP function through their C-terminal appendage domains. By contrast, GGAs are monomers composed of four domains, which have functions similar to AP subunits: an N-terminal VHS (Vps27p/Hrs/Stam) domain, a GAT (GGA and Tom1) domain, a hinge region, and a C-terminal GAE (gamma-adaptin ear) domain. The GAE domain is similar to the AP gamma-adaptin ear domain, being responsible for the recruitment of accessory proteins that regulate clathrin-mediated endocytosis [PMID: 12858162]. While clathrin mediates endocytic protein transport from ER to Golgi, coatomers (COPI, COPII) primarily mediate intra-Golgi transport, as well as the reverse Golgi to ER transport of dilysine-tagged proteins [PMID: 14690497]. Coatomers reversibly associate with Golgi (non-clathrin-coated) vesicles to mediate protein transport and for budding from Golgi membranes [PMID: 17041781]. Coatomer complexes are hetero-oligomers composed of at least an alpha, beta, beta', gamma, delta, epsilon and zeta subunits. This entry represents the N-terminal domain of various adaptins from different AP clathrin adaptor complexes (including AP1, AP2, AP3 and AP4), and from the beta and gamma subunits of various coatomer (COP) adaptors. This domain has a 2-layer alpha/alpha fold that forms a right-handed superhelix, and is a member of the ARM repeat superfamily [PMID: 12086608]. The N-terminal region of the various AP adaptor proteins share strong sequence identity; by contrast, the C-terminal domains of different adaptins share similar structural folds, but have little sequence identity [PMID: 2495531]. It has been proposed that the N-terminal domain interacts with another uniform component of the coated vesicles.