Nucleosome structure: Difference between revisions
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== | [[es:Nucleosome structure (Spanish)]] | ||
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<Structure load='1aoi' size='450' frame='true' align='right' caption='Nucleosome [[1aoi]]' scene='60/602771/Nucleosoma/3'/> | |||
<big><big>'''Nucleosomes''' are the basic building blocks of '''chromatin fibers'''. A nucleosome consists of a core containing '''an octamer of histone proteins''' and a '''DNA''' molecule 146 bp long wound around this core in two complete turns. | |||
The <scene name='60/602771/Proteinas/5'>histone protein octamer</scene> includes four types of proteins: <scene name='60/602771/Histonah2a/1'>H2A</scene>, <scene name='60/602771/Histonah2b/1'>H2B</scene>, <scene name='60/602771/Histonah3/1'>H3</scene> and <scene name='60/602771/Histonah4/1'>H4</scene>. Histone proteins are organized in dimers so: | |||
- | *Two H3-H4 dimers | ||
< | **<scene name='60/602771/Dimeroh3h4-1/1'>H3-H4 dimer (1)</scene> | ||
< | **<scene name='60/602771/Dimeroh3h4-2/1'>H3-H4 dimer (2)</scene> | ||
*Two H2A-H2B dimers | |||
**<scene name='60/602771/Dimeroh2a-h2b-1/1'>H2A-H2B dimer (1)</scene> | |||
**<scene name='60/602771/Dimeroh2a-h2b-2/1'>H2A-H2B dimer (2)</scene> | |||
*<scene name='60/602771/Octamero/1'>Whole octamer</scene> | |||
*<scene name='60/602771/Nucleosoma/3'>DNA</scene> molecule wound in <scene name='60/602771/Nucleosoma/4'>two complete turns</scene> around octamer. Some <scene name='60/602771/Nucleosoma/5'>manganese ions</scene> complete the whole structure. | |||
The main secondary structure in <scene name='60/602771/Octamero/2'>histones</scene> is <scene name='60/602771/Secondarystructure/1'>alpha helices</scene>. | |||
If we highlight the different types of amino acid residues on the <scene name='60/602771/Esqueleto/1'>protein backbone</scene> we can see that <scene name='60/602771/Residuosnegativos/1'>negatively charged residues</scene> and <scene name='60/602771/Residuospositivos/1'>positively charged residues</scene> are arranged so positively charged residues are in <scene name='60/602771/Periferia/1'>peripheral positions</scene>, where they can form ionic interactions ([[salt bridges]]) with <scene name='60/602771/Interacciones/1'>phosphate groups on the DNA molecule</scene>. This distribution of electric charges stabilizes the whole structure. | |||
<small> | |||
==See Also== | |||
*[[Nucleosome structure (Spanish)]] | |||
*[[Nucleosomes]] | |||
*[[User:Eric Martz/Nucleosomes]] | |||
== References == | == References == | ||
<references/> | <references/> | ||
This page is based on [[1aoi]] file from Proteopedia. | |||
[[1aoi]] is a 10 chain structure with sequence from [http://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis]. The July 2000 RCSB PDB [http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/index.html Molecule of the Month] feature on ''Nucleosome'' by David S. Goodsell is [http://dx.doi.org/10.2210/rcsb_pdb/mom_2000_7 10.2210/rcsb_pdb/mom_2000_7]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AOI OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1AOI FirstGlance]. | [[1aoi]] is a 10 chain structure with sequence from [http://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis]. The July 2000 RCSB PDB [http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/index.html Molecule of the Month] feature on ''Nucleosome'' by David S. Goodsell is [http://dx.doi.org/10.2210/rcsb_pdb/mom_2000_7 10.2210/rcsb_pdb/mom_2000_7]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AOI OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1AOI FirstGlance]. | ||
Latest revision as of 19:21, 2 March 2016
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Nucleosomes are the basic building blocks of chromatin fibers. A nucleosome consists of a core containing an octamer of histone proteins and a DNA molecule 146 bp long wound around this core in two complete turns. The histone protein octamer includes four types of proteins: H2A, H2B, H3 and H4. Histone proteins are organized in dimers so:
- Two H3-H4 dimers
- Two H2A-H2B dimers
- Whole octamer
- DNA molecule wound in two complete turns around octamer. Some manganese ions complete the whole structure.
The main secondary structure in histones is alpha helices.
If we highlight the different types of amino acid residues on the protein backbone we can see that negatively charged residues and positively charged residues are arranged so positively charged residues are in peripheral positions, where they can form ionic interactions (salt bridges) with phosphate groups on the DNA molecule. This distribution of electric charges stabilizes the whole structure.
See Also
References
This page is based on 1aoi file from Proteopedia.
1aoi is a 10 chain structure with sequence from Xenopus laevis. The July 2000 RCSB PDB Molecule of the Month feature on Nucleosome by David S. Goodsell is 10.2210/rcsb_pdb/mom_2000_7. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
