Adaptins are proteins that mediate the formation of vesicles by clathrin

Clathrin

Clathrin is a protein that plays a major role in the formation of coated vesicles. Clathrin was first isolated and named by Barbara Pearse in 1975. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice...

-coated pits, through interaction with membrane-bound receptor

Receptor (biochemistry)

In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

s. There are several types of adaptin, each related to a different group of such receptors.

Adaptins show sequence similarity to some COPI

COPI

COPI is a protein complex that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum , where they were originally synthesized and between golgi compartments. This type of transport is termed as retrograde transport...

 subunits, thus they are thought to have a common evolutionary origin.

Adaptins cluster to form the AP2 complex

AP2 adaptors

The AP2 adaptor complex is a multimeric protein that works on the plasma membrane to internalize cargo in clathrin-mediated endocytosis. It is a stable complex of four adaptins which give rise to a structure that has a core domain and two appendage domains attached to the core domain by polypeptide...

.

The Adaptin complex is a heterotetramer consisting of two large adaptins (alpha or beta), a medium adaptin (mu), and a small adaptin (sigma):

• complex 1
  • AP1B1
  • AP1G1
    AP1G1
    AP-1 complex subunit gamma-1 is a protein that in humans is encoded by the AP1G1 gene.-Interactions:AP1G1 has been shown to interact with RABEP1, AP1B1, Synaptophysin, AP1M1, NECAP2, AP1S1 and AP1GBP1.-Further reading:...
    
    
  • AP1G2
    AP1G2
    AP-1 complex subunit gamma-like 2 is a protein that in humans is encoded by the AP1G2 gene.-Further reading:...
    
    
  • AP1M1
    AP1M1
    AP-1 complex subunit mu-1 is a protein that in humans is encoded by the AP1M1 gene.-Interactions:AP1M1 has been shown to interact with VAMP4 and AP1G1.-Further reading:...
    
    
  • AP1M2
    AP1M2
    AP-1 complex subunit mu-2 is a protein that in humans is encoded by the AP1M2 gene.-Further reading:...
    
    
  • AP1S1
    AP1S1
    AP-1 complex subunit sigma-1A is a protein that in humans is encoded by the AP1S1 gene.A mutation in the AP1S1 causes the rare familial MEDNIK syndrome described in 2008.-Interactions:AP1S1 has been shown to interact with AP1G1 and RAB10....
    
    
  • AP1S2
    AP1S2
    AP-1 complex subunit sigma-2 is a protein that in humans is encoded by the AP1S2 gene.-Further reading:...
    
    
  • AP1S3
• complex 2
  • AP2A1
    AP2A1
    AP-2 complex subunit alpha-1 is a protein that in humans is encoded by the AP2A1 gene.-Interactions:Adaptor-related protein complex 2, alpha 1 has been shown to interact with DPYSL2 and NUMB.-Further reading:...
    
    
  • AP2A2
    AP2A2
    AP-2 complex subunit alpha-2 is a protein that in humans is encoded by the AP2A2 gene.-Interactions:AP2A2 has been shown to interact with EPN1 and SHC1.-Further reading:...
    
    
  • AP2B1
    AP2B1
    AP-2 complex subunit beta is a protein that in humans is encoded by the AP2B1 gene.-Interactions:AP2B1 has been shown to interact with TGF beta receptor 2, AP1M2, BUB1B, LDLRAP1 and Arrestin beta 2.-Further reading:...
    
    
  • AP2M1
    AP2M1
    AP-2 complex subunit mu is a protein that in humans is encoded by the AP2M1 gene.-Interactions:AP2M1 has been shown to interact with CTLA-4 and Alpha-1B adrenergic receptor.-Further reading:...
    
    
  • AP2S1
    AP2S1
    AP-2 complex subunit sigma is a protein that in humans is encoded by the AP2S1 gene.-Further reading:...
    
    
• complex 3
  • AP3B1
    AP3B1
    AP-3 complex subunit beta-1 is a protein that in humans is encoded by the AP3B1 gene.-External Links:* -Further reading:...
    
    
  • AP3B2
    AP3B2
    AP-3 complex subunit beta-2 is a protein that in humans is encoded by the AP3B2 gene.-Further reading:...
    
    
  • AP3M1
    AP3M1
    AP-3 complex subunit mu-1 is a protein that in humans is encoded by the AP3M1 gene.-Further reading:...
    
    
  • AP3M2
  • AP3S1
    AP3S1
    AP-3 complex subunit sigma-1 is a protein that in humans is encoded by the AP3S1 gene.-Further reading:...
    
    
  • AP3S2
    AP3S2
    AP-3 complex subunit sigma-2 is a protein that in humans is encoded by the AP3S2 gene.-Further reading:...
    
    
• complex 4
  • AP4B1
    AP4B1
    AP-4 complex subunit beta-1 is a protein that in humans is encoded by the AP4B1 gene.-Clinical relevance:It is currently hypothesized that AP4-complex-mediated trafficking plays a crucial role in brain development and functioning.-Further reading:...
    
    
  • AP4E1
    AP4E1
    AP-4 complex subunit epsilon-1 is a protein that in humans is encoded by the AP4E1 gene.- Function :The heterotetrameric adaptor protein complexes sort integral membrane proteins at various stages of the endocytic and secretory pathways...
    
    
  • AP4M1
    AP4M1
    AP-4 complex subunit mu-1 is a protein that in humans is encoded by the AP4M1 gene.-Clinical relevance:It is currently hypothesized that AP4-complex-mediated trafficking plays a crucial role in brain development and functioning.-Further reading:...
    
    
  • AP4S1
    AP4S1
    AP-4 complex subunit sigma-1 is a protein that in humans is encoded by the AP4S1 gene.- Function :The heterotetrameric adaptor protein complexes sort integral membrane proteins at various stages of the endocytic and secretory pathways...