Figure 3. Structural transition of RfaH-CTD.
(A) Ribbon diagram of a representative RfaH-CTD structure, residues 101–162, termini and secondary structure elements are labeled. Orientation relative to Figure 1 is indicated.
(B) Ensemble of 20 accepted lowest energy structures. The flexible part, residues 101 107, is indicated.
(C) Ribbon representation of NusG-CTD (PDB-ID: 2JVV (Mooney et al., 2009b)). Residues in the hydrophobic core of the CTD, sticks; carbon, magenta; oxygen, red; nitrogen, blue; sulfur, yellow.
(D) RfaH-CTD (PDB-ID: 2OUG (Belogurov et al., 2007)) in the all α-helical conformation; residues corresponding to the NusG-CTD core, magenta sticks. Within the α-helical RfaH-CTD these residues are scattered randomly along the helices (middle). For residues P110 and F159, no electron density could be determined in the full-length protein (Belogurov et al., 2007); therefore, these are excluded. Domain opening leads to drastic refolding of RfaH-CTD (right) into an all β-barrel state; the residues corresponding to the NusG-CTD core also form the refolded RfaH-CTD core.