The domain within your query sequence starts at position 138 and ends at position 239; the E-value for the BACK domain shown below is 3.93e-27.

CLDMQDFAEAFSCSGLASAAQRFILRHVGELGAEQLERLPLARLLRYLRDDGLCVPKEEA
AYQLALRWVRADPPRRAPHWPQLLEAVRLPFVRRFYLLAHVE

BACK

BTB And C-terminal Kelch

• SMART accession number: SM00875
• Description: The BACK domain is found juxtaposed to the BTB domain; they are separated by as little as two residues.
• Interpro abstract (IPR011705):

  This domain is found associated with ( IPR000210 ) and ( IPR006652 ). BTB (broad-complex, tramtrack and bric a brac) is a Kelch related domain, also known as the POZ domain [ (PUBMED:16207353) ]. BTB proteins are divided into subgroups depending on what domain lies at the C terminus. Despite the divergence in sequences, the BTB fold is highly conserved.

  BTB-Kelch proteins have Kelch repeats that form a beta-propeller that can interact with actin filaments [ (PUBMED:15544948) ]. BTB and C-terminal Kelch (BACK) together constitute a novel conserved domain, which is thought to have a possible role in substrate orientation in Cullin3-based E3 ligase complexes.

  Four domains, namely the BTB domain, a kelch domain, a BACK domain, and an intervening region (IVR) make up the aryl hydrocarbon receptor (AHR); a ligand-activated transcription factor [ (PUBMED:16582008) ]. This entry represents the domain associated with BTB and Kelch.

There are 27812 BACK domains in 27689 proteins in SMART's nrdb database.

Cellular role (predicted cellular role)

Cellular role: interaction

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Stogios PJ, Prive GG
• The BACK domain in BTB-kelch proteins.
• Trends Biochem Sci. 2004; 29: 634-7

A novel conserved motif--the BACK (for BTB and C-terminal Kelch)domain--is found in the majority of proteins that contain both the BTBdomain and kelch repeats. Many kelch-repeat proteins are involved inorganization of the cytoskeleton via interaction with actin andintermediate filaments, whereas BTB domains have multiple cellular roles,including recruitment to E3 ubiquitin ligase complexes. The identificationof the BACK domain in BTB and kelch proteins, and its high conservationacross metazoan genomes, suggest an important function for this domainwith a possible role in substrate orientation in Cullin3-based E3 ligasecomplexes.

Metabolism (metabolic pathways involving proteins which contain this domain)

% proteins involved	KEGG pathway ID	Description
90.00	map04120	Ubiquitin mediated proteolysis
5.00	map00020	Citrate cycle (TCA cycle)
5.00	map00720	Reductive carboxylate cycle (CO2 fixation)

This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with BACK domain which could be assigned to a KEGG orthologous group, and not all proteins containing BACK domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.

Structure (3D structures containing this domain)

3D Structures of BACK domains in PDB

PDB code	Title
2eqx	Solution structure of the BACK domain of Kelch repeat and BTB domain-containing protein 4
3hve	Structures of SPOP-Substrate Complexes: Insights into Molecular Architectures of BTB-Cul3 Ubiquitin Ligases: GigaxoninBTB/3-box
3i3n	Crystal structure of the BTB-BACK domains of human KLHL11
4ap2	Crystal structure of the human KLHL11-Cul3 complex at 2.8A resolution
4apf	Crystal structure of the human KLHL11-Cul3 complex at 3.1A resolution
4hxi	Crystal structure of KLHL3/Cul3 complex

Links (links to other resources describing this domain)

• PFAM: BACK
• INTERPRO: IPR011705