BTB/POZ domain
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The BTB/POZ domain (BTB for BR-C, ttk and bab
Discovery
The BTB/POZ domain was first described by two independent research groups in 1994. Researchers at UCLA found a conserved 115 amino acid motif in nine Drosophila proteins, including Broad complex, tramtrack, and bric-a-brac, and labelled the conserved region the BTB domain.[2] At the same time, a group at Imperial Cancer Research Fund Laboratories in London discovered the same 120 amino acid motif in a set of otherwise unrelated zinc finger proteins and a set of pox-virus proteins, and thus named the region the POZ domain.[3]
Structure
The motif is approximately 120 amino acids long, with a core fold of 95 amino acids that form five alpha helices and three beta sheets.[4] The alpha helices form two hairpin structures, A1/A2 and A4/A5, out of the first and second and the fourth and fifth alpha helices respectively. The remaining alpha helix, A3, bridges the two. The three beta sheets cap the A1/A2 hairpin.[4] Additional secondary structures can surround this core fold. For example, BTB domains in Kelch proteins, C2H2 zinc finger proteins, and HTH-containing proteins frequently include an additional alpha helix and beta sheet at the N-terminus of the domain.[12]
Function
The BTB domain is primarily a protein-protein interaction domain. In zinc-finger proteins, it commonly forms