Histones are basic proteins that in association with DNA form a structure known as the nucleosome. Nucleosomes help in the condensation of DNA into chromatin inside the eukaryotic nucleus.
The nucleosome consists of four types of histone proteins. They are H2A, H2B, H3, and H4. A total of eight histones proteins are present i.e. 2 each of H2A, H2B, H3, and H4. The histone protein with the lowest molecular weight is H4. The histone H4 has a molecular weight of about ~11 kDa. Others are H1 (~22 kDa), H2A (~14 kDa), H2B (~13 kDa), and H3 (~15 kDa).