Nucleosomes
Nucleosomes are complex structures that constitute the basic unit of Chromatin,
the form of DNA organization in Eukaryota. Nucleosomes are formed by a protein core containing an octamer
of Histones, strongly basic proteins largely conserved through Evolution. The basic character is due
to their high content of Lysine and Arginine, that at the cell pH present positive charge and interact
with the negative charge of phosphates in DNA. The structure of nucleosome is as follows:
The components of nucleosomes are the following: 1. Two copies of H2a histone:
There is another histone, H1 histone, that it is not part of the nucleosome but
interacts with the linker DNA, that connects two succesive nucleosomes.