260d

From Proteopedia

CRYSTAL STRUCTURE OF THE SELF-COMPLEMENTARY 5'-PURINE START DECAMER D(GCACGCGTGC) IN THE A-DNA CONFORMATION-PART II

Overview

The crystal structure of the alternating 5'-purine start decamer d(GCGCGCGCGC) was found to be in the left-handed Z-DNA conformation. Inasmuch as the A.T base pair is known to resist Z-DNA formation, we substituted A.T base pairs in the dyad-related positions of the decamer duplex. The alternating self-complementary decamer d(GCACGCGTGC) crystallizes in a different hexagonal space group, P6(1)22, with very different unit cell dimensions a = b = 38.97 and c = 77.34 A compared with the all-G.C alternating decamer. The A.T-containing decamer has one strand in the asymmetric unit, and because it is isomorphous to some other A-DNA decamers it was considered also to be right-handed. The structure was refined, starting with the atomic coordinates of the A-DNA decamer d(GCGGGCCCGC), by use of 2491 unique reflections out to 1.9-A resolution. The refinement converged to an R value of 18.6% for a total of 202 nucleotide atoms and 32 water molecules. This research further demonstrates that A.T base pairs not only resist the formation of Z-DNA but can also assist the formation of A-DNA by switching the helix handedness when the oligomer starts with a 5'-purine; also, the length of the inner Z-DNA stretch (d(CG)n) is reduced from an octamer to a tetramer. It may be noted that these oligonucleotide properties are in crystals and not necessarily in solutions.

About this Structure

260D is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.

Reference

Crystal structure of the self-complementary 5'-purine start decamer d(GCACGCGTGC) in the A-DNA conformation. II., Ban C, Sundaralingam M, Biophys J. 1996 Sep;71(3):1222-7. PMID:8873996

Page seeded by OCA on Mon Mar 31 01:45:34 2008