Nucleosome structure
From Proteopedia
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| - | [[es:Nucleosome structure ( | + | [[es:Nucleosome structure (Spanish)]] |
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| - | <Structure load='1aoi' size=' | + | <Structure load='1aoi' size='450' frame='true' align='right' caption='Nucleosome [[1aoi]]' scene='60/602771/Nucleosoma/3'/> |
| - | <big><big>''' | + | <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 | *Two H3-H4 dimers | ||
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*<scene name='60/602771/Octamero/1'>Whole octamer</scene> | *<scene name='60/602771/Octamero/1'>Whole octamer</scene> | ||
| - | *<scene name='60/602771/Nucleosoma/3'>DNA</scene> molecule <scene name='60/602771/Nucleosoma/4'> | + | *<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>. | |
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| + | 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. | ||
| - | Si localizamos los distintos tipos de residuos de aminoácidos a lo largo del <scene name='60/602771/Esqueleto/1'>esqueleto</scene> de las proteínas histónicas podemos comprobar que los <scene name='60/602771/Residuosnegativos/1'>residuos con carga negativa</scene> y los <scene name='60/602771/Residuospositivos/1'>residuos con carga positiva</scene> se disponen de manera que estos últimos, en la periferia del <scene name='60/602771/Periferia/1'>octámero</scene>, pueden establecer interacciónes electrostáticas con las cargas negativas de <scene name='60/602771/Interacciones/1'>los grupos fosfato en la molécula de DNA</scene>. Tal distribución de cargas positivas y negativas, y las interacciones iónicas que entre ellas tienen lugar, confiere una gran estabilidad al conjunto de la estructura. | ||
<small> | <small> | ||
| + | ==See Also== | ||
| + | *[[Nucleosome structure (Spanish)]] | ||
| + | *[[Nucleosomes]] | ||
| + | *[[User:Eric Martz/Nucleosomes]] | ||
| + | |||
== References == | == References == | ||
<references/> | <references/> | ||
Current revision
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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 includes four types of proteins: , , and . Histone proteins are organized in dimers so:
- Two H3-H4 dimers
- Two H2A-H2B dimers
- molecule wound in around octamer. Some complete the whole structure.
The main secondary structure in is .
If we highlight the different types of amino acid residues on the we can see that and are arranged so positively charged residues are in , where they can form ionic interactions (salt bridges) with . 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.
