Figure 2.

A) Dimerization of α subunits (α₁: yellow, α₂: green). Structural domains and linkers for connecting the αNTD and αCTD are indicated. Amino acid residues contacting with the β and the β’ are highlighted in cyan and pink, respectively. Amino acid residues of αNTD responsible for the interaction with CAP are highlighted in blue. Arg265 in the αCTD for the UP element DNA interaction is shown in red color CPK representation. B) Structural model of the CAP (light blue), RNAP (core enzyme, white; σ⁷⁰, orange) and lac promoter DNA complex (PDB: 6B6H). The CAP binds DNA centered at position −61.5 relative to the transcription start site (+1) and interacts with one copy of the αCTD positioning between the CAP and σ⁷⁰. A linker (236-247 residues) connecting between the NTD and CTD of α subunit is shown as yellow line.