<P> In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes . They are the chief protein components of chromatin, acting as spools around which DNA winds, and playing a role in gene regulation . Without histones, the unwound DNA in chromosomes would be very long (a length to width ratio of more than 10 million to 1 in human DNA). For example, each human diploid cell (containing 23 pairs of chromosomes) has about 1.8 meters of DNA; wound on the histones, the diploid cell has about 90 micrometers (0.09 mm) of chromatin . When the diploid cells are duplicated and condensed during mitosis, the result is about 120 micrometers of chromosomes . </P> <Table> <Tr> <Th_colspan="2"> Core histone H2A / H2B / H3 / H4 </Th> </Tr> <Tr> <Td_colspan="2"> PDB rendering of Complex between nucleosome core particle (h3, h4, h2a, h2b) and 146 bp long DNA fragment based on 1aoi . </Td> </Tr> <Tr> <Th_colspan="2"> Identifiers </Th> </Tr> <Tr> <Th> Symbol </Th> <Td> Histone </Td> </Tr> <Tr> <Th> Pfam </Th> <Td> PF00125 </Td> </Tr> <Tr> <Th> Pfam clan </Th> <Td> CL0012 </Td> </Tr> <Tr> <Th> InterPro </Th> <Td> IPR007125 </Td> </Tr> <Tr> <Th> SCOP </Th> <Td> 1hio </Td> </Tr> <Tr> <Th> SUPERFAMILY </Th> <Td> 1hio </Td> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Th_colspan="2"> show Available protein structures: </Th> </Tr> <Tr> <Th> Pfam </Th> <Td> structures </Td> </Tr> <Tr> <Th> PDB </Th> <Td> RCSB PDB; PDBe; PDBj </Td> </Tr> <Tr> <Th> PDBsum </Th> <Td> structure summary </Td> </Tr> </Table> </Td> </Tr> </Table>

What is the difference between histone and nonhistone protein
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