AbrB-like transcription factors assume a swapped hairpin fold that is evolutionarily related to double-psi beta barrels.
Coles, M., Djuranovic, S., Soding, J., Frickey, T., Koretke, K., Truffault, V., Martin, J., Lupas, A.N.(2005) Structure 13: 919-928
- PubMed: 15939023 
- DOI: 10.1016/j.str.2005.03.017
- Primary Citation of Related Structures:  
1YFB, 1YSF - PubMed Abstract: 
AbrB is a key transition-state regulator of Bacillus subtilis. Based on the conservation of a betaalphabeta structural unit, we proposed a beta barrel fold for its DNA binding domain, similar to, but topologically distinct from, double-psi beta barrels. However, the NMR structure revealed a novel fold, the "looped-hinge helix ...