FIGURE 9-29 Interaction of bacteriophage 434 repressor with DNA. Ribbon diagram of 434 repressor bound to its specific operator DNA. The recognition helices are shown in green. The α helices N-terminal to the recognition helix and the turn in the polypeptide backbone between the helices in the helix-turn-helix structural motif are shown in yellow and red, respectively. The protein interacts intimately with one side of the DNA molecule over a length of 1.5 turns.

[Data from A. K. Aggarwal et al., 1988, Science 242:899, PDB ID 2ori.]