Z-DNA: Difference between revisions
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'''Z-DNA''' <scene name='Z-DNA/Z-dna_new/1'>(default scene)</scene> is a form of DNA that has a different structure from the more common <scene name='Sandbox_Z-DNA/Bdna/3'>B-DNA</scene> form.It is a left-handed double helix wherein the sugar-phosphate backbone has a zigzag pattern due to the alternate stacking of bases in [http://proteopedia.org/wiki/index.php/Syn_and_anti_nucleosides anti-conformation and syn conformation]. In Z-DNA only a minor groove is present and the major groove is absent. The residues that allow sequence-specific recognition of Z-DNA are present on the convex outer surface.<ref name = 'Rich'> PMID:12838348</ref> This DNA form is thought to play a role in the regulation of gene expression, DNA processing events and/or genetic instability.<ref name = 'Wang'>PMID:17485386</ref> | '''Z-DNA''' <scene name='Z-DNA/Z-dna_new/1'>(default scene)</scene> is a form of DNA that has a different structure from the more common <scene name='Sandbox_Z-DNA/Bdna/3'>B-DNA</scene> form.It is a left-handed double helix wherein the sugar-phosphate backbone has a zigzag pattern due to the alternate stacking of bases in [http://proteopedia.org/wiki/index.php/Syn_and_anti_nucleosides anti-conformation and syn conformation]. In Z-DNA only a minor groove is present and the major groove is absent. The residues that allow sequence-specific recognition of Z-DNA are present on the convex outer surface.<ref name = 'Rich'> PMID:12838348</ref> This DNA form is thought to play a role in the regulation of gene expression, DNA processing events and/or genetic instability.<ref name = 'Wang'>PMID:17485386</ref> | ||
See also [[Z-DNA model tour]]. | |||
== Structure == | == Structure == | ||
Z-DNA (<scene name='Sandbox_Z-DNA/B-z/7'>B-Z DNA junction</scene>, PDB entry [[2acj]]) can form '' | Z-DNA (<scene name='Sandbox_Z-DNA/B-z/7'>B-Z DNA junction</scene>, PDB entry [[2acj]]) can form ''in vitro'' from B-DNA by raising negative super helical stress or under low salt conditions when deoxycytosine is 5-methylated. The formation of Z-DNA ''in vivo'' is an energy requiring process. It forms behind a RNA polymerase moving through a DNA double helix during transcription and is subsequently stabilized due to the generation of negative supercoils. Z-DNA is the first single crystal X-ray structure of a DNA fragment. It was crystallized as a self complementary DNA hexamer d(CG)<sub>3</sub> by Andrew Wang, Alexander Rich and their co-workers at MIT in 1979. <ref name = 'Rich'>PMID:12838348</ref><ref name ='Wang'>PMID:17485386</ref> | ||
Whenever B-DNA transforms into Z-DNA two <scene name='Sandbox_Z-DNA/B-zjunction/7'>B-Z junctions</scene> form. The crystal structure of these junctions revealed<scene name='Sandbox_Z-DNA/Extruded/12'> two extruded bases</scene>, <scene name='Z-DNA/Extruded/2'>adenine</scene> and <scene name='Z-DNA/Extruded/3'>thymine</scene> at the junction. A crucial finding from this structure is that a right handed DNA can transform to a left handed DNA or vice versa by the disruption and extrusion of a base pair. It has also been suggested that the extruded base pairs at B-Z DNA junction may be sites for DNA modification.<ref>PMID:16237447</ref> | Whenever B-DNA transforms into Z-DNA two <scene name='Sandbox_Z-DNA/B-zjunction/7'>B-Z junctions</scene> form. The crystal structure of these junctions revealed<scene name='Sandbox_Z-DNA/Extruded/12'> two extruded bases</scene>, <scene name='Z-DNA/Extruded/2'>adenine</scene> and <scene name='Z-DNA/Extruded/3'>thymine</scene> at the junction. A crucial finding from this structure is that a right handed DNA can transform to a left handed DNA or vice versa by the disruption and extrusion of a base pair. It has also been suggested that the extruded base pairs at B-Z DNA junction may be sites for DNA modification.<ref>PMID:16237447</ref> | ||
