Superfamily: C-terminal, effector domain of the bipartite response regulators

binds to DNA and RNA polymerase; the N-terminal, receiver domain belongs to the CheY family

Lineage:

1. Root: scop
2. Class: All alpha proteins
3. Fold: DNA/RNA-binding 3-helical bundle
   core: 3-helices; bundle, closed or partly opened, right-handed twist; up-and down
4. Superfamily: C-terminal, effector domain of the bipartite response regulators
   binds to DNA and RNA polymerase; the N-terminal, receiver domain belongs to the CheY family

Families:

1. PhoB-like (2)
   contains 4-stranded meander beta-sheet in the N-terminal extension
2. Nitrate/nitrite response regulator (NARL) (1)
   contains additional, fourth helix in the C-terminal extension
3. SpoOA (1)
   elaborated with additional helices