The response regulator Spo0A is comprised of a phophoacceptor domain and a transcription activation domain. This domain corresponds to the transcription activation domain and forms an alpha helical structure comprising of 6 alpha helices. The structure contains a helix-turn-helix and binds DNA [1][2].

1: The trans-activation domain of the sporulation response regulator Spo0A revealed by X-ray crystallography. Lewis RJ, Krzywda S, Brannigan JA, Turkenburg JP, Muchova K, Dodson EJ, Barak I, Wilkinson AJ; Mol Microbiol. 2000;38:198-212. PMID:11069648

2: DNA complexed structure of the key transcription factor initiating development in sporulating bacteria. Zhao H, Msadek T, Zapf J, Madhusudan, Hoch JA, Varughese KI; Structure. 2002;10:1041-1050. PMID:12176382