Interaction between DNA and proteins

A) Structure of the nucleosome

The nucleosome is the structural unit of genetic material in the eukaryotic nucleus: chromatin and chromosomes.

1. Nucleosome

B) DNA-binding motifs in proteins

Some three-dimensional structures appear repeated in different proteins and are responsible of their interaction with specific sequences in DNA.
These structures are called "structural motifs".
They are particularly important for proteins called transcription factors.
The major motifs responsible for interaction with DNA are:

2. Helix-turn-helix
3. Helix-loop-helix
4. Homeodomain
5. Leucine zipper
6. Zinc finger