title: Biophysics of left-handed Z-DNA.
abstract: Substantial new information in the past several years has been reported on different types of DNA structures and the possible biological consequences of these conformations. Detailed X-ray crystallographic analyses have provided a good understanding of several types of DNA structures. Biochemical studies demonstrated the concept of DNA microheterogeneity, i.e., the realization that more than one conformation can exist in a given DNA molecule. This mandates the presence of conformational junctions. Most cellular DNA is believed to exist in a right-handed structure. However, left-handed helices are stabilized by supercoiling. The energetics of the transition reveal a delicate balance between right-handed structures and left-handed helices. Several types of sequences adopt left-handed structures and several of these are known to serve as recombination hot spots. The Hha I restriction enzyme and methylase do not act on left-handed DNA, thus these agents may be used as probes for left-handed helices within suitable sequences. Furthermore, B-Z-DNA junctions contain few if any, non-paired bases at physiological superhelical densities.
mesh_terms: D001483:Base Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D004247:DNA / Q000235:genetics; D004262:DNA Restriction Enzymes; D004278:DNA, Superhelical; D015252:Deoxyribonucleases, Type II Site-Specific; D004734:Energy Metabolism; D006801:Humans; D008745:Methylation; D009690:Nucleic Acid Conformation; D011995:Recombination, Genetic
chemical_list: D004278:DNA, Superhelical; D004247:DNA; D004262:DNA Restriction Enzymes; D015252:Deoxyribonucleases, Type II Site-Specific; C037130:GCGC-specific type II deoxyribonucleases