Ku protein: Difference between revisions
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<StructureSection load='1JEY' size=' | <StructureSection load='1JEY' size='350' side='right' caption='Structure of the Ku heterodimer bound to DNA (PDB entry [[1jey]])' scene='56/567269/Ku_heterodimer/4'> | ||
== Overview == | == Overview == | ||
The '''Ku protein''' binds to the ends of double-strand breaks and it is required in DNA-repair for non-homologous end joining. The eukaryotic Ku protein is a | The '''Ku protein''' or '''X-ray repair cross-complementing protein''' binds to the ends of double-strand breaks and it is required in DNA-repair for non-homologous end joining. The eukaryotic Ku protein is a | ||
<scene name='56/567269/Ku_heterodimer/3'>heterodimer</scene> | <scene name='56/567269/Ku_heterodimer/3'>heterodimer</scene> | ||
composed of a | composed of a | ||
<scene name='56/567269/Ku70_subunit/3'>Ku70 subunit</scene> | <scene name='56/567269/Ku70_subunit/3'>Ku70 subunit</scene> or '''X-ray repair cross-complementing protein 6''' | ||
and a <scene name='56/567269/Ku80_subunit/3'>Ku80 subunit</scene> | and a <scene name='56/567269/Ku80_subunit/3'>Ku80 subunit</scene> or '''X-ray repair cross-complementing protein 5''' | ||
. This contributes to genomic integrity through its ability to bind DNA double-strand breaks and facilitate repair by the non-homologous end-joining pathway. The crystal structure of the human Ku heterodimer was determined both alone and | . This contributes to genomic integrity through its ability to bind DNA double-strand breaks and facilitate repair by the non-homologous end-joining pathway. The crystal structure of the human Ku heterodimer was determined both alone and | ||
<scene name='56/567269/Bound_dna/3'>bound to a 55-nucleotide DNA</scene> | <scene name='56/567269/Bound_dna/3'>bound to a 55-nucleotide DNA</scene> | ||
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This asymmetry leads to different favorable locations for DNA based on major and minor grooves.<ref name="Walker"/> | This asymmetry leads to different favorable locations for DNA based on major and minor grooves.<ref name="Walker"/> | ||
The Ku70 subunit is <scene name='56/567269/Ku70_subunit/5'>angled closer</scene> to DNA at the double strand break, providing protection and interaction with its domains.<ref name="source2"> PMID: 19715578</ref> | The Ku70 subunit is <scene name='56/567269/Ku70_subunit/5'>angled closer</scene> to DNA at the double strand break, providing protection and interaction with its domains.<ref name="source2"> PMID: 19715578</ref> | ||
In contrast, the Ku80 subunit <scene name='56/567269/Ku80_subunit/ | In contrast, the Ku80 subunit <scene name='56/567269/Ku80_subunit/5'>associates with</scene> DNA away from the free end.<ref name="Walker"/> Once a homodimer, the protein has diverged into two domains that are now 15% similar in residues. <ref name="source3"> PMID: 9663392</ref> | ||
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In terms of protein structure, the α/β-Domain contributes little to the dimer interface between the subunits. | In terms of protein structure, the α/β-Domain contributes little to the dimer interface between the subunits. | ||
The C terminus of the domain can be bound to other repair molecules, using the α/β-Domain as a scaffold.<ref name="Walker"/> | The C terminus of the domain can be bound to other repair molecules, using the α/β-Domain as a scaffold.<ref name="Walker"/> | ||
=== β-barrel === | === β-barrel === | ||
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The <scene name='56/567269/Ku70_dimer/4'>β-barrel</scene> is the main source of interactions of the Ku heterodimer itself and DNA helix, with each β-barrel being composed of seven β strands with the majority in antiparallel arrangement.<ref name="Walker"/> | The <scene name='56/567269/Ku70_dimer/4'>β-barrel</scene> is the main source of interactions of the Ku heterodimer itself and DNA helix, with each β-barrel being composed of seven β strands with the majority in antiparallel arrangement.<ref name="Walker"/> | ||
The quantity of the strands lends the structures to be symmetrical. Both β-barrel in the dimer form the base of the cradle by fitting in the grooves of DNA. | The quantity of the strands lends the structures to be symmetrical. Both β-barrel in the dimer form the base of the cradle by fitting in the grooves of DNA. | ||
=== C-terminal arm === | === C-terminal arm === | ||
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The <scene name='56/567269/Ku70_dimer/7'>C-terminal arm</scene> is an α-helical domain that associates with the β-barrel of the opposite subunit, with the arm stretching across the DNA helix.<ref name="Walker"/> | The <scene name='56/567269/Ku70_dimer/7'>C-terminal arm</scene> is an α-helical domain that associates with the β-barrel of the opposite subunit, with the arm stretching across the DNA helix.<ref name="Walker"/> | ||
As a result, the C-terminal arm strengthens the cradle composed of the two β-barrels. | As a result, the C-terminal arm strengthens the cradle composed of the two β-barrels. | ||
=== DNA binding ring === | === DNA binding ring === | ||
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By binding DNA, Ku realigns the the strands and protects the molecule from degradation and unwanted bonds while NHEJ occurs.<ref name="Walker"/> | By binding DNA, Ku realigns the the strands and protects the molecule from degradation and unwanted bonds while NHEJ occurs.<ref name="Walker"/> | ||
The regulation of the DNA binding ring of Ku is still under research, with data supporting oxidative stress and redox reactions decreasing the association of the Ku heterodimer with bound DNA through alterations in cysteine residues on the Ku70 subunit. <ref name="source3"/> <ref name="source4"> PMID: 14585978</ref> | The regulation of the DNA binding ring of Ku is still under research, with data supporting oxidative stress and redox reactions decreasing the association of the Ku heterodimer with bound DNA through alterations in cysteine residues on the Ku70 subunit. <ref name="source3"/> <ref name="source4"> PMID: 14585978</ref> | ||
== Function == | == Function == | ||
The <scene name='56/567269/Ku_heterodimer/3'>Ku heterodimer</scene> serves to assist in [http://en.wikipedia.org/wiki/Non-homologous_end_joining non-homologous end joining (NHEJ)], and also in telomere synthesis and protection. These functions are separate interactions based on key residues that are being identified through current research. Recent research also links the Ku protein with heterochromatin formation through interaction with [http://en.wikipedia.org/wiki/Rif_(GTPase) Rif proteins] and [http://en.wikipedia.org/wiki/Sir2 Sir proteins]. <ref name="source3"/><ref name="source4"/> | The <scene name='56/567269/Ku_heterodimer/3'>Ku heterodimer</scene> serves to assist in [http://en.wikipedia.org/wiki/Non-homologous_end_joining non-homologous end joining (NHEJ)], and also in telomere synthesis and protection. These functions are separate interactions based on key residues that are being identified through current research. Recent research also links the Ku protein with heterochromatin formation through interaction with [http://en.wikipedia.org/wiki/Rif_(GTPase) Rif proteins] and [http://en.wikipedia.org/wiki/Sir2 Sir proteins]. <ref name="source3"/><ref name="source4"/> | ||
<ref>Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman and, 2012. [http://www.whfreeman.com/Catalog/product/biochemistry-seventhedition-berg ISBN-10: 1-4292-2936-5]</ref> | |||
</StructureSection> | |||
== 3D Structures of Ku protein == | |||
Updated on {{REVISIONDAY2}}-{{MONTHNAME|{{REVISIONMONTH}}}}-{{REVISIONYEAR}} | |||
</ | [[1jey]], [[5y58]] – hKu70 + Ku80 + DNA – human<br /> | ||
[[1jeq]] – hKu70 + Ku80 <br /> | |||
[[7axz]] – hKu70 + Ku80 – Cryo EM<br /> | |||
[[6zh6]] – hKu80 + DNA-dependent protein kinase – Cryo EM<br /> | |||
[[7k0y]], [[7k1j]], [[7k1k]], [[7k1n]] – hKu70 + Ku80 + DNA-dependent protein kinase – Cryo EM<br /> | |||
[[6erf]], [[6erg]], [[6erh]] – hKu70 + Ku80 + non-homologous end-joining factor + DNA <br /> | |||
[[1jjr]] – hKu70 C terminal - NMR <br /> | |||
[[1rw2]], [[1q2z]] – hKu80 C terminal - NMR <br /> | |||
[[6tyt]], [[6tyu]], [[6tyv]], [[6tyw]], [[6tyx]], [[6tyz]] – hKu80 von Willebrand domain 1-242 (mutant) + peptide <br /> | |||
[[7lt3]] – hKu70 + Ku80 in NHEJ synaptic complex – Cryo EM<br /> | |||
== References== | == References== | ||
<references /> | <references /> | ||
[[Category:Topic Page]] | |||