Crystal structure of T4 RegA. In panel A, the RegA dimer (pymol rendering of PDB 1REG; ) is labeled at relevant structures discussed in the text. Panel B highlights the likely RNA binding residues in α helix 1 (K14, T18, R21) and loop residue W81. Also shown is the F106 residue that cross-links to bound RNA and is adjacent to the RNA binding region. See Figure 3 for the relative conservation of the labeled amino acids in other RegA proteins. Adapted from the data of [66, 70, 72].