Z-DNA
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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。
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
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
| 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° | 0° |
| 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
- ^ 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
- ^ 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.
- ^ Sinden, Richard R. DNA structure and function 1st. Academic Press. 1994-01-15: 398. ISBN 0-126-45750-6.
- ^ 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.
- ^ 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.