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. Author manuscript; available in PMC: 2015 Apr 1.
Published in final edited form as: Curr Opin Genet Dev. 2014 Jan 24;0:8–14. doi: 10.1016/j.gde.2013.11.006

Figure 1.

Figure 1

Histone-like proteins are found in every kingdom of life and serve to regulate access to the genome, paritally through formation of tertiary structure. In panel A, the co-crystal structure of the HU protein from Anabena and DNA (PDB ID 1P78) shows the HU protein dimer binding the DNA duplex. Panel B shows the crystal structure of the HmfA homodimer from Methanothermus fervidus (PDB ID 1B67) while panel C shows the crystal structure of HmfB (PDB ID 1A7W), also from Methanothermus fervidus. The crystal structure of the fused doublet HmfA from Methanopyrus kandleri (PBD ID 1F1E) is shown in panel D. In panel E, the crystal structure of the canonical eukaryotic histones (PDB ID 1AOI) shows the assembly of the histone octamer, the protein core of the nucleosome. Nucleosomes were previously thought to form 30 nm solenoid fibers as shown in panel F, through recent evidence suggests the genome exists primarily as a 10 nm “beads-on-a-string” fiber, as shown in panel G, with some regions of higher order organization like those shown in panel H.