| B2-adapt-app_C | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 beta2-adaptin appendage domain, from clathrin adaptor ap2 | |||||||||
| Identifiers | |||||||||
| Symbol | B2-adapt-app_C | ||||||||
| Pfam | PF09066 | ||||||||
| InterPro | IPR015151 | ||||||||
| SCOP2 | 1e42 / SCOPe / SUPFAM | ||||||||
| |||||||||
The C-terminal domain ofBeta2-adaptin is a protein domain is involved in cell trafficking by aiding import and export of substances in and out of the cell.
This is an adaptor protein which helps the formation of a clathrin coat around a vesicle.
This entry represents a subdomain of the appendage (ear) domain of beta-adaptin from AP clathrin adaptor complexes. This domain has a three-layer arrangement, alpha-beta-alpha, with a bifurcated antiparallel beta-sheet. [1] This domain is required for binding to clathrin, and its subsequent polymerisation. Furthermore, a hydrophobic patch present in the domain also binds to a subset of D-phi-F/W motif-containing proteins that are bound by the alpha-adaptin appendage domain (epsin, AP180, eps15). [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. These vesicles have specific coat proteins (such as clathrin or coatomer) that are important for cargo selection and direction of transport. [3] 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. [4] [5]
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. [6] AP2 associates with the plasma membrane and is responsible for endocytosis. [7] AP3 is responsible for protein trafficking to lysosomes and other related organelles. [8] 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. [9] One function of clathrin and AP2 complex-mediated endocytosis is to regulate the number of GABA(A) receptors available at the cell surface . [10]
More information about these proteins can be found at Protein of the Month: 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 1976. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice that surrounds the vesicle, hence the protein's name, which is derived from the Latin clathrum meaning lattice. Coat-proteins, like clathrin, are used to build small vesicles in order to transport molecules within cells. The endocytosis and exocytosis of vesicles allows cells to communicate, to transfer nutrients, to import signaling receptors, to mediate an immune response after sampling the extracellular world, and to clean up the cell debris left by tissue inflammation. The endocytic pathway can be hijacked by viruses and other pathogens in order to gain entry to the cell during infection.
Vesicular transport adaptor proteins are proteins involved in forming complexes that function in the trafficking of molecules from one subcellular location to another. These complexes concentrate the correct cargo molecules in vesicles that bud or extrude off of one organelle and travel to another location, where the cargo is delivered. While some of the details of how these adaptor proteins achieve their trafficking specificity has been worked out, there is still much to be learned.
The AP2 adaptor complex is a multimeric protein that works on the cell 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 linkers. These appendage domains are sometimes called 'ears'. The core domain binds to the membrane and to cargo destined for internalisation. The alpha and beta appendage domains bind to accessory proteins and to clathrin. Their interactions allow the temporal and spatial regulation of the assembly of clathrin-coated vesicles and their endocytosis.
ADP-ribosylation factor-binding protein GGA1 is a protein that in humans is encoded by the GGA1 gene.
AP-2 complex subunit mu is a protein that in humans is encoded by the AP2M1 gene.
AP-2 complex subunit alpha-1 is a protein that in humans is encoded by the AP2A1 gene.
AP-1 complex subunit mu-1 is a protein that in humans is encoded by the AP1M1 gene.
AP-1 complex subunit gamma-1 is a protein that in humans is encoded by the AP1G1 gene.
AP-2 complex subunit alpha-2 is a protein that in humans is encoded by the AP2A2 gene.
AP-1 complex subunit beta-1 is a protein that in humans is encoded by the AP1B1 gene.
AP-2 complex subunit beta is a protein that in humans is encoded by the AP2B1 gene.
AP-1 complex subunit sigma-1A is a protein that in humans is encoded by the AP1S1 gene.
Adaptor-associated protein kinase 1 also known as AP2-associated protein kinase 1 is an enzyme that in humans is encoded by the AAK1 gene and is involved in clathrin mediated endocytosis. Alternatively spliced transcript variants have been described, but their biological validity has not been determined.
AP-1 complex subunit gamma-like 2 is a protein that in humans is encoded by the AP1G2 gene.
AP-3 complex subunit mu-1 is a protein that in humans is encoded by the AP3M1 gene.
AP-1 complex subunit sigma-2 is a protein that in humans is encoded by the AP1S2 gene.
Synergin gamma also known as AP1 subunit gamma-binding protein 1 (AP1GBP1) is a protein that in humans is encoded by the SYNRG gene.
Epsin-1 is a protein that in humans is encoded by the EPN1 gene.
AP-2 complex subunit sigma is a protein that in humans is encoded by the AP2S1 gene.
Clathrin adaptor proteins, also known as adaptins, are vesicular transport adaptor proteins associated with clathrin. These proteins are synthesized in the ribosomes, processed in the endoplasmic reticulum and transported from the Golgi apparatus to the trans-Golgi network, and from there via small carrier vesicles to their final destination compartment. The association between adaptins and clathrin are important for vesicular cargo selection and transporting. 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. Therefore, adaptor proteins are responsible for the recruitment of cargo molecules into a growing clathrin-coated pits. The two major types of clathrin adaptor complexes are the heterotetrameric vesicular transport adaptor proteins (AP1-5), and the monomeric GGA adaptors. Adaptins are distantly related to the other main type of vesicular transport proteins, the coatomer subunits, sharing between 16% and 26% of their amino acid sequence.
