1mf5
From Proteopedia
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GCATGCT Quadruplex
Overview
Here we report the crystal structure of the DNA heptanucleotide sequence d(GCATGCT) determined to a resolution of 1.1 A. The sequence folds into a complementary loop structure generating several unusual base pairings and is stabilised through cobalt hexammine and highly defined water sites. The single stranded loop is bound together through the G(N2)-C(O2) intra-strand H-bonds for the available G/C residues, which form further Watson-Crick pairings to a complementary sequence, through 2-fold symmetry, generating a pair of non-planar quadruplexes at the heart of the structure. Further, four adenine residues stack in pairs at one end, H-bonding through their N7-N6 positions, and are additionally stabilised through two highly conserved water positions at the structural terminus. This conformation is achieved through the rotation of the central thymine base at the pinnacle of the loop structure, where it stacks with an adjacent thymine residue within the lattice. The crystal packing yields two halved biological units, each related across a 2-fold symmetry axis spanning a cobalt hexammine residue between them, which stabilises the quadruplex structure through H-bonds to the phosphate oxygens and localised hydration.
About this Structure
1MF5 is a Protein complex structure of sequences from [1] with as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of the complementary quadruplex formed by d(GCATGCT) at atomic resolution., Thorpe JH, Teixeira SC, Gale BC, Cardin CJ, Nucleic Acids Res. 2003 Feb 1;31(3):844-9. PMID:12560479
Page seeded by OCA on Thu Feb 21 13:54:38 2008
