Forms of DNA
From Proteopedia
See Also: Z-DNA
A comparative representation of the three forms of DNA
Sources[1]
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Synchronize the three applets showing A-, B- and Z-DNA by clicking the checkbox
Helical Parameters of the three forms of DNA
DNA is a very flexible molecule and has the ability to exist in various forms based on the environmental conditions. Naturally occurring DNA double helices are classified into A, B and Z-types. A and B-forms of DNA are the right handed forms whereas Z-DNA is the left handed form. When hydrated the DNA generally assumes B-form. The A conformation is found when there is little water to interact with the helix and is also the conformation adopted by the RNA. The formation of Z-DNA occurs with the methylation of deoxycytosine residues and also during transcription where negative supercoiling stabilizes it.
| Parameter | A-DNA | B-DNA | Z-DNA |
|---|---|---|---|
| Helix sense | right-handed | right-handed | left-handed |
| Residues per turn | 11 | 10.5 | 12 |
| Axial rise [Å] | 2.55 | 3.4 | 3.7 |
| Helix pitch(°) | 28 | 34 | 45 |
| Base pair tilt(°) | 20 | −6 | 7 |
| Rotation per residue (°) | 33 | 36 | -30 |
| Diameter of helix [Å] | 23 | 20 | 18 |
| Glycosidic bond configuration dA,dT,dC dG | anti anti | anti anti | anti syn |
| Sugar pucker dA,dT,dC dG | C3'-endo C3'-endo | C2'-endo C2'-endo | C2'-endo C3'-endo |
| Intrastrand phosphate-phosphate distance [Å] dA,dT,dC dG | 5.9 5.9 | 7.0 7.0 | 7.0 5.9 |
| Sources:[2][3][4] | |||
Structural Transformation between A and B DNA
| Drag the structure with the mouse to rotate |
Morph Sources [5]
Proteopedia Page Contributors and Editors (what is this?)
Angel Herraez, Jaime Prilusky, Michal Harel, Adithya Sagar, Eran Hodis, Karsten Theis, Joel L. Sussman, Eric Martz
