434 Phage Repressor

trp Repressor

Zinc Fingers


GAL4 DNA-Binding Domain

Leucine Zipper



Learning Objectives
  1. To understand the overall structural features of helix-turn-helix, zinc finger, and leucine zipper motifs in DNA-binding proteins.
  2. To understand the similarities and differences in these motifs in different transcription factors.


Compare the three-dimensional structures of transcription factor-DNA complexes ("Helix-Turn-Helix", "Zinc-Fingers", or "Leucine Zipper"). Click and drag either of the two members shown for each family to rotate the corresponding representation in 3-D.

  1. How many zinc finger motifs are present in Zif268?
  2. Which secondary structure is used by all six transcription factors shown here to bind to the major groove of DNA?
  3. Which transcription factor would you predict, on the basis of the structure of the DNA-bound complex, to recognize a longer DNA sequence, 434 phage repressor or GCN4?
  4. What is the function of the leucine zipper?