Structure of the histone-core octamer in KCl/phosphate crystals at 2.15 Å resolution

Chantalat, L.; Nicholson, J.M.; Lambert, S.J.; Reid, A.J.; Donovan, M.J.; Reynolds, C.D.; Wood, C.M.; Baldwin, J.P.

doi:10.1107/S0907444903011880

Figure 3
The packing of histone octamers in space group P6₅ crystals. The colour coding is common for all parts of the figures. The αC helices of the histones H2B and H2B′ are magenta and the αN helices of the histones H3 and H3′ are yellow in Figs. 3

(a), 3

(e) and 3

(f). (a) The packing diagram viewed down c. The unit cell (a, b) is outlined. (b) The centre of the packing diagram enlarged. The octamers form left-handed helices, such as the helix shown in cyan, which interpenetrate to form the inter-octamer contacts AB, BA, CD and DC for each octamer as indicated. Each octamer is part of a helix about the centre of a solvent channel having the corresponding colour. The αC helices of histones H2B and H2B′ are shown in magenta in the figure, but only those helices for the H2Bs (as opposed to the H2B′s) are visible, facing the solvent channels. (c) and (d) DNA was positioned onto the histone octamers using the program LSQKAB (Kabsch, 1976

) to relocate the DNA of the nucleosome-core particle accurately onto the histone octamer described herein. The figures highlight the areas of the inter-octamer contact regions, A (green), B (cyan), C (red) and D (blue) for the inter-octamer interactions. Note that whereas the AB interactions in the smaller contact area are exclusively between regions on the unprimed-histone face of the octamer (Fig. 3

c), the CD interactions in the larger contact area are exclusively on the primed-histone face (Fig. 3

d). (e) and (f). The figures show the relative orientations of the octamers in the smaller (AB) (Fig. 3

e) and larger (CD) (Fig. 3

f) interactions. The small green spheres in the interacting regions represent chloride ions and the red cross in Fig. 3

(e) indicates the position of the phosphate. Note the red acidic region on the right-hand surface and the blue basic region on the left-hand surface of Fig. 3

(f) (see Table 2

for details).

BIOLOGICAL
CRYSTALLOGRAPHY

ISSN: 1399-0047

Volume 59| Part 8| July 2003| Pages 1395-1407

doi:10.1107/S0907444903011880

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