In molecular biology, BAR domains are highly conserved protein dimerisation domains that occur in many proteins involved in membrane dynamics in a cell. The BAR domain is banana-shaped and binds to membrane via its concave face. It is capable of sensing membrane curvature by binding preferentially to curved membranes. BAR domains are named after three proteins that they are found in: Bin,

Amphiphysin Amphiphysin is a protein that in humans is encoded by the ''AMPH'' gene. Function This gene encodes a protein associated with the cytoplasmic surface of synaptic vesicles. A subset of patients with stiff person syndrome who were also affected ...

and Rvs.

BAR domains occur in combinations with other domains

Many BAR family proteins contain alternative lipid specificity domains that help target these protein to particular membrane compartments. Some also have

SH3 domain The SRC Homology 3 Domain (or SH3 domain) is a small protein domain of about 60 amino acid residues. Initially, SH3 was described as a conserved sequence in the viral adaptor protein v-Crk. This domain is also present in the molecules of phos ...

s that bind to

dynamin Dynamin is a GTPase responsible for endocytosis in the eukaryotic cell. Dynamin is part of the " dynamin superfamily", which includes classical dynamins, dynamin-like proteins, Mx proteins, OPA1, mitofusins, and GBPs. Members of the dynamin fa ...

and thus proteins like amphiphysin and endophilin are implicated in the orchestration of vesicle scission.

N-BAR domain

Some BAR domain containing proteins have an N-terminal amphipathic helix preceding the BAR domain. This helix inserts (like in the epsin ENTH domain) into the membrane and induces curvature, which is stabilised by the BAR dimer. Amphiphysin, endophilin, BRAP1/bin2 and nadrin are examples of such proteins containing an N-BAR. The Drosophila amphiphysin N-BAR (DA-N-BAR) is an example of a protein with a preference for negatively charged surfaces.

Human proteins containing this domain

AMPH; ARHGAP17;

ARHGAP44 Rho GTPase activating protein 44 is a protein in humans that is encoded by the ARHGAP44 gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''gener ...

;

BIN1 Myc box-dependent-interacting protein 1, also known as Bridging Integrator-1 and Amphiphysin-2 is a protein that in humans is encoded by the ''BIN1'' gene. This gene encodes several isoforms of a nucleocytoplasmic adaptor protein, one of which w ...

; BIN2; BIN3; SH3BP1; SH3GL1;

SH3GL2 Endophilin-A1 is a protein that in humans is encoded by the ''SH3GL2'' gene. Interactions SH3GL2 has been shown to interact with DNM1, Amphiphysin, ADAM9, SH3KBP1 SH3 domain-containing kinase-binding protein 1 (synonyms - CIN85, in rodents - Ru ...

; SH3GL3;

SH3GLB1 Endophilin-B1 is a protein that in humans is encoded by the ''SH3GLB1'' gene. Endophilin-B1 belongs to the Bin/Amphiphysin/Rvs167 ( BAR) family of proteins and plays a critical role in mitochondrial fission and fusion, as well as in autophagy and ...

;

SH3GLB2 Endophilin-B2 is a protein that in humans is encoded by the ''SH3GLB2'' gene. Interactions SH3GLB2 has been shown to interact with SH3GLB1 and SH3KBP1 SH3 domain-containing kinase-binding protein 1 (synonyms - CIN85, in rodents - Ruk) is an ...

F-BAR (EFC) domain

F-BAR domains (for FCH-BAR, or EFC for Extended FCH Homology) are BAR domains that are extensions of the already established FCH domain. They are frequently found at the amino terminus of proteins. They can bind lipid membranes and can tubulate lipids in vitro and in vivo, but their exact physiological role still is under investigation. Examples of the F-BAR domain family are CIP4/FBP17/Toca-1, Syndapins (also called PACSINs) and

muniscins The muniscin protein family was initially defined in 2009 as proteins having 2 homologous domains that are involved in clathrin mediated endocytosis Endocytosis is a cellular process in which substances are brought into the cell. The material ...

. Gene knock-out of syndapin I in mice revealed that this brain-enriched isoform of the syndapin family is crucial for proper size control of synaptic vesicles and thereby indeed helps to define

membrane curvature Membrane curvature is the geometrical measure or characterization of the curvature of membranes. The membranes can be naturally occurring or man-made (synthetic). An example of naturally occurring membrane is the lipid bilayer of cells, also known ...

a physiological process. Work of the lab of Britta Qualmann also demonstrated that syndapin I is crucial for proper targeting of the large GTPase

to membranes.

Sorting nexins

The

sorting nexin Sorting nexins are a large group of proteins that are localized in the cytoplasm and have the potential for membrane association either through their lipid-binding PX domain (a phospholipid-binding motif) or through protein–protein inter ...

family of proteins includes several members that possess a BAR domain, including the well characterized

SNX1 Sorting nexin-1 is a protein that in humans is encoded by the SNX1 gene. The protein encoded by this gene is a sorting nexin. SNX1 is a component of the retromer complex. Function This gene encodes a member of the sorting nexin family. Memb ...

and

SNX9 Sorting nexin-9 is a protein that in humans is encoded by the ''SNX9'' gene. This gene encodes a member of the sorting nexin family. Members of this family contain a phox (PX) domain, which is a phosphoinositide binding domain, and are involved i ...

Human proteins containing this domain

AMPH; ARHGAP17;

; BIN2; BIN3; DNMBP;

GMIP The Pattani Islamic Mujahideen Movement ( ms, Gerakan Mujahidin Islam Patani; GMIP) is an Islamic insurgent movement that has carried out violent actions as part of the protracted insurgency in Southern Thailand. GMIP is hostile to the practice ...

; RICH2; SH3BP1; SH3GL1;

; SH3GL3;

;

External links

endocytosis.org

BAR domains occur in combinations with other domains

N-BAR domain

Human proteins containing this domain

F-BAR (EFC) domain

Sorting nexins

Human proteins containing this domain

See also

External links

References

Further reading