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Symmetry in Nucleic-Acid Double Helices

Crystallography, Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
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Symmetry 2020, 12(5), 737; https://doi.org/10.3390/sym12050737
Received: 1 April 2020 / Revised: 17 April 2020 / Accepted: 20 April 2020 / Published: 5 May 2020
(This article belongs to the Special Issue Symmetry in Molecular Biology)
In nature and in the test tube, nucleic acids occur in many different forms. Apart from single-stranded, coiled molecules, DNA and RNA prefer to form helical arrangements, in which the bases are stacked to shield their hydrophobic surfaces and expose their polar edges. Focusing on double helices, we describe the crucial role played by symmetry in shaping DNA and RNA structure. The base pairs in nucleic-acid double helices display rotational pseudo-symmetry. In the Watson–Crick base pairs found in naturally occurring DNA and RNA duplexes, the symmetry axis lies in the base-pair plane, giving rise to two different helical grooves. In contrast, anti-Watson–Crick base pairs have a dyad axis perpendicular to the base-pair plane and identical grooves. In combination with the base-pair symmetry, the syn/anti conformation of paired nucleotides determines the parallel or antiparallel strand orientation of double helices. DNA and RNA duplexes in nature are exclusively antiparallel. Watson–Crick base-paired DNA or RNA helices display either right-handed or left-handed helical (pseudo-) symmetry. Genomic DNA is usually in the right-handed B-form, and RNA double helices adopt the right-handed A-conformation. Finally, there is a higher level of helical symmetry in superhelical DNA in which B-form double strands are intertwined in a right- or left-handed sense. View Full-Text
Keywords: DNA; RNA; double helix; base-pair symmetry; pseudo-symmetry; Watson-Crick base pair; base-pair stacking; nucleotide conformation; X-ray fiber diffraction; X-ray crystallography DNA; RNA; double helix; base-pair symmetry; pseudo-symmetry; Watson-Crick base pair; base-pair stacking; nucleotide conformation; X-ray fiber diffraction; X-ray crystallography
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MDPI and ACS Style

Heinemann, U.; Roske, Y. Symmetry in Nucleic-Acid Double Helices. Symmetry 2020, 12, 737.

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