Figure 8.

Core histone protein structure and sequence evolution. (a) Structural relationships between the four core histone protein families. (b) Three-dimensional nucleosome structure is shown with each core histone chain colored: H2A, orange; H2B, yellow; H3, blue; and H4, green. (c) Sequence relationships within and between the four core histone protein families. Internal nodes that set-off each core histone family are color coded using the same scheme used for the nucleosome structure. The tree is rooted with archaeal histone-like sequences (white internal node).