Sandbox Z-DNA
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Z-DNA is relatively a new structural form of a DNA which has a different structure from the more common B-DNA form.It is a left-handed double helix wherein the sugar-phosphate backbone has a zigzag pattern.Hence the name Z-DNA.The zigzag pattern is due to the alternate stacking of bases in 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 [Herbert et.al.,]. Z-DNA is thought play a role in regulation of gene expression, DNA processing events and/or genetic instability [Wang et.al .,].
StructureStructure
Z-DNA can form invitro from B-DNA by raising negative super helical stress or under physiological salt conditions when deoxycytosine is 5-methylated [Herbert8]. The formation of Z-DNA which requires energy is an active process invivo. A mechanism for initiation of Z-DNA involves formation of negative supercoils behind a moving RNA polymerase when it moves through DNA double helix [Herbert 16]. `