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[[File:Z-DNA orbit animated small.gif|right|frame|Z-DNA結構。]]

'''Z-DNA'''又稱'''Z型DNA'''，是DNA雙螺旋結構的一種形式，具有左旋型態的雙股螺旋（與常見的[[B-DNA]]相反），並呈現鋸齒形狀。Z-DNA為三種具生物活性的DNA雙螺旋結構之一，另兩種為[[A-DNA]]與B-DNA。

== 歷史 ==
Z-DNA為首先於1979年被解出晶體結構的DNA型態，研究者為[[麻省理工大學]]的Alexander Rich等人<ref name=Wang1979>{{cite journal en|author=Wang AHJ, Quigley GJ, Kolpak FJ, Crawford JL, van Boom JH, Van der Marel G, Rich A |title=Molecular structure of a left-handed double helical DNA fragment at atomic resolution |journal=Nature (London) |volume=282 |pages=680-686 |year=1979}} PMID 514347</ref>。B型及Z型相互結合時的結晶則解於2005年<ref name=Ha2005>{{cite journal en|author=Ha SC, Lowenhaupt K, Rich A, Kim YG, Kim KK |title=Crystal structure of a junction between B-DNA and Z-DNA reveals two extruded bases |url=https://archive.org/details/sim_nature-uk_2005-10-20_437_7062/page/1182 |journal=Nature |volume=437 |pages=1183-1186 |year=2005 |id=PMID 16237447}}</ref>，使科學家了解Z-DNA在細胞中的潛在角色，當一段Z-DNA形成時，其兩端必為B-Z相互結合型態，形成與B-DNA的介面。

== 結構 ==
[[File:B-, Z-DNA junction 2ACJ.png|right|thumb|300px|B-DNA（深藍色）與Z-DNA（深紅色）相互結合型態，以及Z-DNA結合區塊（綠色），可見其兩個的突出的鹼基（中央的淡藍色及淡紅色）。來自{{PDB|2ACJ}}。]]
Z-DNA的雙股螺旋為左旋型態，與B-DNA的右旋型態明顯有所差別。其結構每兩個鹼基對重複出現一次。大小螺旋凹槽之間的差別較A型及B型小，只在寬度上有些微差異。這種型態並不常見，但某些特定情況可增加其存在的可能，如[[嘌呤]]-[[嘧啶]]交替序列、[[DNA超螺旋]]，或鹽份與某些[[陽離子]]濃度高時。

Z-DNA能夠與B-DNA構成相互結合型態，這種結構會使一對鹼基突出於雙螺旋之外。

==一些DNA形式幾何形狀的對比==
[[Image:A-DNA, B-DNA and Z-DNA.png|right|thumb|A-, B-, 與 Z-DNA的側視圖.]]
[[Image:B&Z&A DNA formula.svg|thumb|right|250px|A-, B-, 與 Z-DNA的螺旋軸.]]
{| class="wikitable"
|-
!幾何屬性
!A-DNA
!B-DNA
!Z-DNA
|-
|螺旋方向 ||align="center"| 右旋 ||align="center"| 右旋 ||align="center"| 左旋
|-
|重複單元 ||align="right"| 1 bp ||align="right"| 1 bp ||align="right"| 2 bp
|-
|Rotation/bp ||align="right"| 32.7° ||align="right"| 35.9° ||align="right"| 60°/2
|-
|bp/turn ||align="right"| 11.6 ||align="right"| 10.5 ||align="right"| 12
|-
|Inclination of bp to axis ||align="right"| +19° ||align="right"| −1.2° ||align="right"| −9°
|-
|Rise/bp along axis ||align="right"| 2.3 Å (0.23 nm)||align="right"| 3.32 Å (0.332 nm)||align="right"| 3.8 Å (0.38 nm)
|-
|Pitch/turn of helix ||align="right"| 28.2 Å (2.82 nm)||align="right"| 33.2 Å (3.32 nm)||align="right"| 45.6 Å (4.56 nm)
|-
|Mean propeller twist ||align="right"| +18° ||align="right"| +16° ||align="right"| 0°
|-
|糖基角度 ||align="center"| anti ||align="center"| anti ||align="center"| C: anti,<br> G: syn
|-
|Sugar pucker ||align="center"| C3'-endo ||align="center"| C2'-endo ||align="center"| C: C2'-endo,<br>G: C3'-endo
|-
|直徑 ||align="right"| 23 Å (2.3 nm)||align="right"| 20 Å (2.0 nm)||align="right"| 18 Å (1.8 nm)
|-
|colspan="4"|''來源:<ref name="Sinden1994">{{cite book
|title=DNA structure and function
|last=Sinden
|first=Richard R
|date=1994-01-15
|publisher=Academic Press
|edition=1st
|isbn=0-126-45750-6
|pages=398}}</ref><ref name="Rich1984">{{cite journal
|author=Rich A, Norheim A, Wang AHJ
|title=The chemistry and biology of left-handed Z-DNA
|journal=Annual Review of Biochemistry
|volume=53
|issue=1
|pages=791–846
|year=1984
|doi=10.1146/annurev.bi.53.070184.004043
|pmid=6383204}}</ref><ref name="pmid7937803">{{cite journal |doi=10.1073/pnas.91.20.9549 |author=Ho PS |title=The non-B-DNA structure of d(CA/TG)n does not differ from that of Z-DNA |journal=Proc Natl Acad Sci USA |date=1994-09-27 |volume=91 |issue=20 |pages=9549–9553 |pmid=7937803 |pmc=44850|bibcode = 1994PNAS...91.9549H }}</ref>''
|}

== 參見 ==
*[[DNA的機械性質]]
*[[DNA]]
*[[A-DNA]]
*[[B-DNA]]

== 參考文獻 ==
<references/>

=== 延伸閱讀 ===
* Sinden RR (1994). DNA structure and function. ''Academic Press'', 179-216. ISBN 978-0-12-645750-6
* Rich A, Zhang S (2003). Timeline: Z-DNA: the long road to biological function. ''Nat Rev Genet, 4:566–572''.
== 外部連結 ==
* [https://web.archive.org/web/20071105012741/http://gac-web.cgrb.oregonstate.edu/zDNA/ ZHunt Online Server]

{{Nucleic acids}}

[[Category:DNA]]

Z-DNA - 版本历史

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