Nucleic Acids Research, 2005, Vol. 33, No. 10 3431 Figure 4. Crystal packing of human NCP. (A) The upper stereo model shows the human NCP crystal packing, viewed approximately perpendicular to the crystallographic c-axis. The bottom figure displays the side view of the same molecular arrangements. Short arrows show the approximate locations of the three crystallographic axes. Only the DNA backbone is shown for clarity. The pink, orange and green circles are equivalent with the regions illustrated by those in Figures 2A and Figures 3A and B. The black arrows indicate the directions and ranges of the consecutive 1 bp shifts to the 30-side. (B–D) The close-up stereo views of the boxed area in (A) show the discrepancy in the DNA structures by the superposition between human (yellow) and X.laevis (light blue; PDB code 1KX3) (11) NCPs, based on the histone octamers alone. The gray arrows represent the modification of the DNA pathway by the inter-particle collides.