Final answer:
Histone proteins H2A, H2B, H3, and H4 form the core of the nucleosome around which DNA wraps. Histone H1 is associated with linker DNA. Together, these proteins package DNA into a compact structure and regulate gene access and expression.
Step-by-step explanation:
The histone proteins involved in the formation of the nucleosome are H2A, H2B, H3, and H4. Each nucleosome core particle consists of an octamer composed of two molecules each of these four histone types. Wrapped around this octamer is approximately 147 base pairs of negatively charged DNA, which is attracted to the positively charged histone due to the abundance of lysine and arginine amino acids. A fifth histone, H1, is associated with the linker DNA, which connects adjacent nucleosomes and helps compact the nucleosome structure into the higher-order 30 nm fiber.
Histone H2A and Histone H2B, along with H3 and H4, are fundamental to the chromatin structure by forming the nucleosome bead, around which the DNA winds, effectively packaging it and playing a role in regulating gene expression.
During chromatin compaction, these nucleosomes are further organized with the help of non-histone proteins, leading to more condensed structures such as heterochromatin and euchromatin, depending on gene expression levels.