1i9k | pdb_00001i9k

THE RNA I-MOTIF

spinqualitylabelsall models 1i9k, 1 NMR models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1i9k is a 4 chain structure. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Oligodeoxynucleotides with stretches of cytidine residues associate into a four-stranded structure, the i-motif, in which two head-to-tail, intercalated, parallel-stranded duplexes are held together by hemiprotonated C.C+ pairs. We have investigated the possibility of forming an i-motif structure with C-rich ribonucleic acids. The four C-rich RNAs studied, r(UC5), r(C5), r(C5U) and r(UC3), associate into multiple intercalated structures at acidic pH. r(UC5) forms two i-motif structures that differ by their intercalation topologies. We report on a structural study of the main form and we analyze the small conformational differences found by comparison with the DNA i-motif. The stacking topology of the main structure avoids one of the six 2'-OH/2'-OH repulsive contacts expected in a fully intercalated structure. The C3'-endo pucker of the RNA sugars and the orientation of the intercalated C.C+ pairs result in a modest widening of the narrow grooves at the steps where the hydroxyl groups are in close contact. The free energy of the RNA i-motif, on average -4 kJ mol(-1) per C.C+ pair, is half of the value found in DNA i-motif structures. The RNA i-motif.,Snoussi K, Nonin-Lecomte S, Leroy JL J Mol Biol. 2001 May 25;309(1):139-53. PMID:11491284 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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