1rme
From Proteopedia
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'''DNA (5'-D(5MCP*CP*TP*CP*C)-3') TETRAMER, NMR, 1 STRUCTURE''' | '''DNA (5'-D(5MCP*CP*TP*CP*C)-3') TETRAMER, NMR, 1 STRUCTURE''' | ||
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==About this Structure== | ==About this Structure== | ||
| - | + | Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1RME OCA]. | |
==Reference== | ==Reference== | ||
Structure and conversion kinetics of a bi-stable DNA i-motif: broken symmetry in the [d(5mCCTCC)]4 tetramer., Nonin S, Leroy JL, J Mol Biol. 1996 Aug 23;261(3):399-414. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/8780782 8780782] | Structure and conversion kinetics of a bi-stable DNA i-motif: broken symmetry in the [d(5mCCTCC)]4 tetramer., Nonin S, Leroy JL, J Mol Biol. 1996 Aug 23;261(3):399-414. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/8780782 8780782] | ||
| - | [[Category: Protein complex]] | ||
[[Category: Leroy, J L.]] | [[Category: Leroy, J L.]] | ||
[[Category: Nonin, S.]] | [[Category: Nonin, S.]] | ||
| - | [[Category: | + | [[Category: Deoxyribonucleic acid]] |
| - | [[Category: | + | [[Category: I-motif]] |
| - | [[Category: | + | [[Category: Tetramer]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 07:40:09 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 04:40, 3 May 2008
DNA (5'-D(5MCP*CP*TP*CP*C)-3') TETRAMER, NMR, 1 STRUCTURE
Overview
At slightly acidic pH, protonation of C-rich oligomers results in the formation of a four-stranded structure composed of two parallel duplexes in a head to tail orientation with their hemi-protonated C.C+ pairs intercalated in a so-called i-motif. In all cases reported previously the duplexes are identical. The tetramer formed by the d(5mCCTCC) oligomer is different. The structure is computed on the basis of 55 inter-residue distances derived from NOESY cross-peaks measured at short mixing times. It consists of two intercalated non-equivalent symmetrical duplexes. The base stacking order is C5* C1 C4* C2 (T3*) T3 C2* C4 C1* C5, but the thymidine bases (T3*) of one duplex are looped out and lie in the wide grooves of the tetramer. The thymidine bases T3 stack as a symmetrical T.T pair between the sequentially adjacent C2.C2+ pair and the C2*.C2*+ pair of the other duplex. Numerous exchange cross-peaks provide evidence for duplex interconversion. The interconversion rate is 1.4 s-1 at 0 degree C and the activation energy is 94 kJ/mol. The opening of the T3.T3 pair, the closing of the T3*.T3 pair, and the opening of the C2*.C2*+ pair occur simultaneously with the duplex interconversion. This suggests that the concerted opening and closing of the thymidine bases drive the duplex interconversion. Opening of the C4.C4+ and C4*.C4*+ pairs, and dissociation of the tetramer are not part of the interconversion since they occur at much slower rates. Duplex interconversion within the [d(5mCCTCC)]4 tetramer provides the first structural and kinetics characterization of broken symmetry in a biopolymer. The tetramer formed by d(5mCCUCC) adopts a similar structure, but the rate of duplex interconversion is faster: 40 s-1 at 0 degree C. At 32 degrees C, interconversion is fast on the NMR time scale.
About this Structure
Full crystallographic information is available from OCA.
Reference
Structure and conversion kinetics of a bi-stable DNA i-motif: broken symmetry in the [d(5mCCTCC)]4 tetramer., Nonin S, Leroy JL, J Mol Biol. 1996 Aug 23;261(3):399-414. PMID:8780782 Page seeded by OCA on Sat May 3 07:40:09 2008
