Members of this family adopt a secondary structure consisting of a pair of long, antiparallel alpha-helices (the stem) that support a three-helix bundle (3HB) at their end. The 3HB contains a helix-turn-helix motif and is similar to the DNA binding domains of the bacterial site-specific recombinases, and of eukaryotic Myb and homeodomain transcription factors. The Tower domain has an important role in the tumour suppressor function of BRCA2, and is essential for appropriate binding of BRCA2 to DNA [1].

1: BRCA2 function in DNA binding and recombination from a BRCA2-DSS1-ssDNA structure. Yang H, Jeffrey PD, Miller J, Kinnucan E, Sun Y, Thoma NH, Zheng N, Chen PL, Lee WH, Pavletich NP; Science 2002;297:1837-1848. PMID:12228710