The C terminal domain of the B transposition protein from Bacteriophage Mu comprises four alpha-helices arranged in a loosely packed bundle, where helix alpha1 runs parallel to alpha3, and anti-parallel to helices alpha2 and alpha4. The domain allows for non-specific binding of Mu to double-stranded DNA, allowing for integration into the bacterial genome, and mediates dimerisation of the protein [1].

1: The solution structure of the C-terminal domain of the Mu B transposition protein. Hung LH, Chaconas G, Shaw GS; EMBO J. 2000;19:5625-5634. PMID:11060014