The mkdom and XDOM programs have been used to analyze the domain organizations of the ArcB, ArcB' and ArcA in E.coli, Haemophilus influenzae and Haemophilus ducreyi.
(Top) ArcB consists of the N-terminal transmembrane domain and a putative leucine zipper (2). The primary transmitter domain (H1) and the receiver domain (D1) are at the central region. And the secondary transmitter domain (H2) (3) (6) is at the C-terminal except Haemophilus ducreyi has the unique ArcB' encoded this H2 domain.
(Bottom) ArcA consists of an N-terminal receiver domain (D2) and a C-terminal helix-turn-helix (HTH) domain (4).