Final answer:
The H1 or linker histone binds to the linker DNA between nucleosomes, aiding in the compact structure of chromatin. It is distinct from the core histones (H2A, H2B, H3, and H4) that form the nucleosome beads and does not form part of the nucleosome core.
Step-by-step explanation:
The histone protein that does not make up the nucleosome bead but instead binds to linker DNA is known as H1 or the linker histone. This protein is associated with the linker DNA that connects adjacent nucleosomes, stabilizing the structure of chromatin. The nucleosome bead is formed by DNA wrapping around a core of eight histone proteins, while the linker DNA connects the nucleosomes.
Nucleosomes consist of a DNA segment wrapped around a core of eight histone proteins, with DNA in a form about seven times shorter than its extended state. The association of H1 with the linker DNA assists in facilitating the higher-order structure of chromatin, including compaction into the 30 nm fiber and ultimately the fully compacted chromosome seen during metaphase.
Unlike the core histones that form the octamer (two each of H2A, H2B, H3, and H4), the H1 histone interacts with the DNA between the nucleosomes and is crucial for the condensation of the chromatin fiber.