Show the:   Proteins, only.   DNA, only.   Whole complex.   Rotate:   X 90°   X -90°   Y 90°   Y -90°   Distances:   Protein core   ( in Å units)   Whole complex   (diam in Å units)   Reset

The Nucleosome Core Particle. Eukaryotic chromatin is organized in a structural hierarchy. The smallest unit is the nucleosome, a complex between ~150 bp of DNA and two copies each of four histones. The DNA strands are colored green and brown. The histone coloring is: H3, blue; H4, light green; H2A, yellow; and H2B, red. Note the "histone-fold" in all four proteins. This is a structural motif comprised of three a-helices connected by two loops (a1-L1-a2-L2-a3). See the close-ups below for how they combine in the heterodimers to form crescent-shaped DNA-binding units. (cf. Fig. 1a of Luger, et al.)   Close-up view of the H3-H4 histone-fold pair.   Highlight:Leu 65 (spacefill). Arg and Lys residues (blue).     (cf. Fig. 2a of Luger, et al.)   Close-up view of the H2A-H2B histone-fold pair.   Highlight: Arg and Lys residues (blue).     (cf. Fig. 2b of Luger, et al.) Viewing tips: Use the buttons to the right of the image to show only portions of the structure; then use the Chime menu to display or color the molecule. The rotate buttons act on the entire structure. Remove the distance monitors with a second click.