FIGURE 9-43 General design of transcription factors in the nuclear-receptor superfamily. The centrally located DNA-binding domain exhibits considerable sequence homology among different receptors and contains two copies of the C₄ zinc-finger motif (see Figure 9-30b). The C-terminal hormone-binding domain exhibits somewhat less homology. The N-terminal regions of various receptors vary in length, have unique sequences, and may contain one or more activation domains. See R. M. Evans, 1988, Science 240:889.