Z-DNA was discovered in vitro under high salt conditions. It is know to exist in the interband regions of the giant salivary gland chromosomes of Drosophila and in the transcriptionally active macronucleus of the ciliated protozoan Stylonchia mytilus. The properties of Z-form DNA are listed below:
1) It is a left-handed helix and the helical diameter is 18Å.
2) There are 12 base pairs per turn in the Z-DNA. Because of the maximum number of base pairs per turn found in this form, the Z-DNA has the least twisted structure.
3) It has a zig-zag sugar phosphate backbone.
4) It has a rise of 0.38 nm per base pair.
5) The Z-form DNA occurs in polymers that have a sequence of alternating purines and pyrimidines (especially Gs and Cs). The alternating polymers could be poly d(GC) or poly d(AC).
6) Instead of having both major and minor grooves, the Z-DNA has only a single groove.
Scientists have raised antibodies specific to Z-DNA (E M Lafer, R P Valle, A Möller, A Nordheim, P H Schur, A Rich, and B D Stollar. J Clin Invest. 1983 February; 71(2): 314–321). The antibodies have helped in the detection of Z-DNA under different cellular conditions (M Robert-Nicoud, D J Arndt-Jovin, D A Zarling, and T M Jovin. EMBO J. 1984 April; 3(4): 721–731).