Structure of the nucleosome

Here you can see the structure of the nucleosome. More precisely, of the so-called nucleosomal core. The whole nucleosome includes an additional histone (H1) and a longer DNA.

Nucleosome:

• Core particle:
  • 200 bp of DNA
  • 2 molecules of H2a histone
  • 2 molecules of H2b histone
  • 2 molecules of H3 histone
  • 2 molecules of H4 histone
• 1 molecule of H1 histone
• 50 bp of DNA

Note how the 8 histone molecules form a tight core, surrounded by the DNA chain, which describes nearly 2 turns around.

in white the DNA ends.
The DNA chain extends from those ends, separating from the core; a molecule of H1 histone interacts with the extension of both ends, like a DNA "clasp" over the nucleosome. The full set { core particle + DNA + H1 } constitutes the whole nucleosome.