Local mobility of nucleic acids as determined from crystallographic data. II. Z-form DNA.
Directions and magnitudes of the local mobility of the Z-DNA hexamer duplex CpGpCpGpCpG have been determined by crystallographic refinement of anisotropic displacement parameters using the observed X-ray diffraction data. The cytidine and guanosine residues demonstrate different modes of mobility, implying that a dinucleotide is the smallest repeating unit in terms of flexibility as well as structure. Directions of librational and translational mobility of the cytidine and guanosine residues of Z-DNA are similar to those observed for the same nucleotides in B-DNA. This suggests that the local mobility of DNA is primarily determined by the individual nucleotide type and by the constraints of Watson-Crick base-pairing, rather than by helical form. Differences in the magnitudes of mobility may be responsible for some of the different physical properties of B-DNA and Z-DNA. The B to Z transition is discussed in terms of the observed flexibilities of these two helical forms.
S R
SR
Holbrook
A H
AH
Wang
A
A
Rich
S H
SH
Kim
D001483:Base Sequence; D003461:Crystallography; D003562:Cytidine; D004247:DNA / Q000235:genetics; D006151:Guanosine; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D014176:Protein Biosynthesis
D009838:Oligodeoxyribonucleotides; D006151:Guanosine; D003562:Cytidine; D004247:DNA