N. Spink et al., CRYSTAL-STRUCTURE OF A DNA DECAMER SHOWING A NOVEL PSEUDO 4-WAY HELIX-HELIX JUNCTION, Proceedings of the National Academy of Sciences of the United Statesof America, 92(23), 1995, pp. 10767-10771
The crystal structure of the decanucleotide d(CGCAATTGCG)(2) has been
solved by a combination of molecular replacement and heavy-atom proced
ures and has been refined to an R factor of 20.2% at 2.7 Angstrom. It
is not a fully base-paired duplex but has a central core of eight Wats
on-Crick base pairs flanked by unpaired terminal guanosines and cytosi
nes. These participate in hydrogen-bonding arrangements with adjacent
decamer duplexes in the crystal lattice. The unpaired guanosines are b
ound in the G+C regions of duplex minor grooves. The cytosines have re
latively high mobility, even though they are constrained to be in one
region where they are involved in base-paired triplets with G-C base p
airs. The 5'-AATT sequence in the duplex region has a narrow minor gro
ove, providing further confirmation of the sequence-dependent nature o
f groove width.