1ybr

Solution structure of the 5'E topology of the i-motif tetramer of d(CCCCAA)

spinqualitylabelsall models 1ybr, 1 NMR models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1ybr is a 4 chain structure. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Related: 294d, 1ybl, 1ybn Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed Using NMR methods, we have resolved the i-motif structures formed by d(AACCCC) and by d(CCCCAA), two versions of the DNA sequence repeated in the telomeric regions of the C-rich strand of tetrahymena chromosomes. Both oligonucleotides form fully symmetrical i-motif tetramers built by intercalation of two hemiprotonated duplexes containing four C*C+ pairs. The structures are extremely stable. In the tetramer of d(AACCCC), the outermost C*C+ pairs are formed by the cytidines of the 5' ends of the cytidine tracts. A2 forms an A2*A2 (H6trans-N7) pair stacked to C3*C3+ and cross-strand stacked to A1. At 0 degrees C, the lifetimes of the hemiprotonated pairs range from 1 ms for the outermost pair to approximately 1 h for the innermost pairs. The tetramer of d(CCCCAA) adopts two distinct intercalation topologies in slow conformational exchange. One, whose outermost C*C+ pairs are built by the cytidines of the 5' end and the other by those of the 3' end. In both topologies, the adenosine bases are fairly well stacked to the adjacent C*C+ pairs. They are not paired but form symmetrical pseudo-pairs with their H6cis amino proton and N1 nitrogen pointing towards each other. i-motif solution structure and dynamics of the d(AACCCC) and d(CCCCAA) tetrahymena telomeric repeats.,Esmaili N, Leroy JL Nucleic Acids Res. 2005 Jan 12;33(1):213-24. Print 2005. PMID:15647504 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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