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The BTB domain (Broad-Complex, Tramtrack and Bric a brac) is also known as the POZ domain (POxvirus and Zinc finger). It is a homodimerization domain occurring at the N-terminus of proteins containing multiple copies of either zinc fingers of the C2H2 type (see <PDOC00028>) or Kelch repeats [1,2]. Many BTB proteins are transcriptional regulators that are thought to act through the control of chromatin structure.

The structure of the BTB domain of the promyelocytic leukemia zinc finger (PLZF) protein has been determined by X-ray crystallography and reveals a tightly intertwined dimer with an extensive hydrophobic interface [3]. A surface-exposed groove lined with conserved amino acids is formed at the dimer interface, suggesting a peptide-binding site.

Some proteins known to contain a BTB/TTK domain are listed below:

• Mammalian Bach proteins. These transcriptional regulators act as repressors or activators.
• Mammalian B-cell lymphoma 6 protein (BCL-6). A transcriptional regulator.
• Mammalian calicin. A possible morphogenic cytoskeletal element in spermiogenic differenciation.
• Human promyelocytic leukemia zinc finger (PLZF). A probable transcription factor.
• Drosophila GAGA transcription factor.
• Drosophila Mod(MDG4) or E(VAR)3-93D. A chromatin protein involved in gene silencing in position effect variegation, the control of gypsy insulator sequence, maintenance of gene expression, and apoptosis.
• Drosophila Tramtrack (TTK) protein. A probable transcriptional repressor.
• Drosophila Kelch protein. A component of ring canals that regulates the flow of cytoplasm between cells.
• Vaccinia virus proteins A55, C2, C4, C13, and F3.
• Myxoma virus proteins M-T8 and M-T9.

December 2001 / First entry.

PROSITE method (with tools and information) covered by this documentation:

BTB, PS50097; BTB domain profile  (MATRIX)

Sequences known to belong to this class detected by the profile: ALL Other sequence(s) detected in Swiss-Prot: NONE

• Domain architecture view of Swiss-Prot proteins matching PS50097 • Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS50097 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS50097 • Scan Swiss-Prot/TrEMBL entries against PS50097 • view ligand binding statistics

Matching PDB structures: 1BUO 1CS3 1R28 1R29 ... [ALL]

1	Authors	Zollman S., Godt D., Prive G.G., Couderc J.L., Laski F.A.
	Title	The BTB domain, found primarily in zinc finger proteins, defines an evolutionarily conserved family that includes several developmentally regulated genes in Drosophila.
	Source	Proc. Natl. Acad. Sci. U.S.A. 91:10717-10721(1994).
	PubMed ID	7938017

2	Authors	Bardwell V.J., Treisman R.
	Title	The POZ domain: a conserved protein-protein interaction motif.
	Source	Genes Dev. 8:1664-1677(1994).
	PubMed ID	7958847

3	Authors	Ahmad K.F., Engel C.K., Prive G.G.
	Title	Crystal structure of the BTB domain from PLZF.
	Source	Proc. Natl. Acad. Sci. U.S.A. 95:12123-12128(1998).
	PubMed ID	9770450

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