Z-DNA又称Z型DNA,是DNA双螺旋结构的一种形式,具有左旋型态的双股螺旋(与常见的B-DNA相反),并呈现锯齿形状。Z-DNA为三种具生物活性的DNA双螺旋结构之一,另两种为A-DNA与B-DNA。

Z-DNA结构。

历史

Z-DNA为首先于1979年被解出晶体结构的DNA型态,研究者为麻省理工大学的Alexander Rich等人[1]。B型及Z型相互结合时的结晶则解于2005年[2],使科学家了解Z-DNA在细胞中的潜在角色,当一段Z-DNA形成时,其两端必为B-Z相互结合型态,形成与B-DNA的界面。

结构

 
B-DNA(深蓝色)与Z-DNA(深红色)相互结合型态,以及Z-DNA结合区块(绿色),可见其两个的突出的碱基(中央的淡蓝色及淡红色)。来自PDB 2ACJ

Z-DNA的双股螺旋为左旋型态,与B-DNA的右旋型态明显有所差别。其结构每两个碱基对重复出现一次。大小螺旋凹槽之间的差别较A型及B型小,只在宽度上有些微差异。这种型态并不常见,但某些特定情况可增加其存在的可能,如嘌呤-嘧啶交替序列、DNA超螺旋,或盐分与某些阳离子浓度高时。

Z-DNA能够与B-DNA构成相互结合型态,这种结构会使一对碱基突出于双螺旋之外。

一些DNA形式几何形状的对比

 
A-, B-, 与 Z-DNA的侧视图.
 
A-, B-, 与 Z-DNA的螺旋轴.
几何属性 A-DNA B-DNA Z-DNA
螺旋方向 右旋 右旋 左旋
重复单元 1 bp 1 bp 2 bp
Rotation/bp 32.7° 35.9° 60°/2
bp/turn 10 11 12
Inclination of bp to axis +19° −1.2° −9°
Rise/bp along axis 2.3 Å (0.23 nm) 3.32 Å (0.332 nm) 3.8 Å (0.38 nm)
Pitch/turn of helix 28.2 Å (2.82 nm) 33.2 Å (3.32 nm) 45.6 Å (4.56 nm)
Mean propeller twist +18° +16°
糖基角度 anti anti C: anti,
G: syn
Sugar pucker C3'-endo C2'-endo C: C2'-endo,
G: C3'-endo
直径 23 Å (2.3 nm) 20 Å (2.0 nm) 18 Å (1.8 nm)
来源:[3][4][5]

参见

参考文献

  1. ^ Wang AHJ, Quigley GJ, Kolpak FJ, Crawford JL, van Boom JH, Van der Marel G, Rich A. Molecular structure of a left-handed double helical DNA fragment at atomic resolution. Nature (London). 1979, 282: 680–686.  PMID 514347
  2. ^ Ha SC, Lowenhaupt K, Rich A, Kim YG, Kim KK. Crystal structure of a junction between B-DNA and Z-DNA reveals two extruded bases. Nature. 2005, 437: 1183–1186. PMID 16237447. 
  3. ^ Sinden, Richard R. DNA structure and function 1st. Academic Press. 1994-01-15: 398. ISBN 0-126-45750-6. 
  4. ^ Rich A, Norheim A, Wang AHJ. The chemistry and biology of left-handed Z-DNA. Annual Review of Biochemistry. 1984, 53 (1): 791–846. PMID 6383204. doi:10.1146/annurev.bi.53.070184.004043. 
  5. ^ Ho PS. The non-B-DNA structure of d(CA/TG)n does not differ from that of Z-DNA. Proc Natl Acad Sci USA. 1994-09-27, 91 (20): 9549–9553. Bibcode:1994PNAS...91.9549H. PMC 44850 . PMID 7937803. doi:10.1073/pnas.91.20.9549. 

延伸阅读

  • 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.

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