Question

Which histone protein is not a part of the nucleosome?

Answer 1

Nucleosomes are the basic packing unit of DNA. It is made by histone protein around DNA which is coiled. Combined tight loop of DNA and protein is called the nucleosome. Fiber of the packed nucleosome is called the chromatin. This nucleosome is present in the nucleus of the eukaryotic cell. Fundamental subunit of chromatin is called the nucleosome.

Complete answer:
Histone protein has two molecules. They have proteins called H$2$A, H$2$B, H$3$ and H$4$. Histone protein H$1$ is not a part of the nucleosome. It connects two nucleosomes along with linker DNA. H$1$ is made by chromatin in eukaryotes. It doesn't make nucleosomes but it is positioned at the top of structure and maintains the position of DNA in the nucleosome. It is presented as a half of the amount compared to others. A One nucleosome consists of two H$1$ histone on top of the structure.
If the H$1$ wants to bind with another nucleus then it needs a linker DNA. During the shortened exposure of DNA, it promotes the solenoid like chromatin fiber. The main function of H$1$ histone is to establish the compaction state of an array of nucleosomes and it is used for the confirmation process. H$1$ has three domains; they are central globular DNA, N and C terminus.

Note:
Histones are the proteins present in the chromosomes. This histone joins with the DNA and provides the shape for chromosomes and helps to control the activity of genes. Histones are composed of positively charged amino acid residues called lysine and arginine. So, this positively charged particle is combined with the negatively charged DNA by the electrostatic interactions.