Mixture of histones H1, H2A, H2B, H3, and H4, isolated from calf thymus.
Histones are a group of DNA-binding proteins that are characterized by relatively high levels of lysine and arginine. Five different fractions of histones have been isolated and characterized. These are named as H1, H2A, H2B, H3 and H4. The H1 fraction is lysine-rich, while the H2A and H2B are slightly lysine-rich, The H3 and H4 fractions are arginine-rich. The molecular weights of histones are approximately 11 to 21 kDa depending on the fraction.