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1a8w

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{{STRUCTURE_1a8w| PDB=1a8w | SCENE= }}
{{STRUCTURE_1a8w| PDB=1a8w | SCENE= }}
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'''A K+ CATION-INDUCED CONFORMATIONAL SWITCH WITHIN A LOOP SPANNING SEGMENT OF A DNA QUADRUPLEX CONTAINING G-G-G-C REPEATS, NMR, 8 STRUCTURES'''
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===A K+ CATION-INDUCED CONFORMATIONAL SWITCH WITHIN A LOOP SPANNING SEGMENT OF A DNA QUADRUPLEX CONTAINING G-G-G-C REPEATS, NMR, 8 STRUCTURES===
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==Overview==
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We have identified a unique structural transition (in slow exchange on the NMR time scale) in the tertiary fold of the d(G-G-G-C-T4-G-G-G-C) quadruplex on proceeding from Na+ to K+ as counterion in aqueous solution. Both monovalent cation-dependent conformations exhibit certain common structural features, which include head-to-tail dimerization of two symmetry-related stem-hairpin loops, adjacent strands which are antiparallel to each other and adjacent stacked G(syn).G(anti). G(syn).G(anti) tetrads in the central core of the quadruplexes. The Na and K cation stabilized structures of the d(G-G-G-C-T4-G-G-G-C) quadruplexes differ in the conformations of the T-T-T-T loops, the relative alignment of G.C base-pairs positioned opposite each other through their major groove edges and potentially in the number of monovalent cation binding sites. We have identified potential K cation binding cavities within the symmetry-related T-T-T-G segments, suggesting the potential for two additional monovalent cation binding sites in the K cation-stabilized quadruplex relative to its Na cation-stabilized counterpart. Modeling studies suggest that the major groove edges of guanine residues in Watson-Crick G.C base-pairs could potentially be bridged by coordinated K cations in the d(G-G-G-C-T4-G-G-G-C) quadruplex in KCl solution in contrast to formation of G.C.G.C tetrads for the corresponding quadruplex in NaCl solution. Our results defining the molecular basis of a Na to K cation-dependent conformational switch in the loop spanning segment of the d(G-G-G-C-T4-G-G-G-C) quadruplex may have relevance to recent observations that specific K cation coordinated loop conformations within quadruplexes exhibit inhibitory activity against HIV integrase.
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(as it appears on PubMed at http://www.pubmed.gov), where 9737927 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9737927}}
==About this Structure==
==About this Structure==
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Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1A8W OCA].
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Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1A8W OCA].
==Reference==
==Reference==
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[[Category: K+ cation encapsulation within a hairpin loop]]
[[Category: K+ cation encapsulation within a hairpin loop]]
[[Category: Monovalent]]
[[Category: Monovalent]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 09:59:39 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 16:23:59 2008''

Revision as of 13:24, 30 June 2008

Image:1a8w.png

Template:STRUCTURE 1a8w

A K+ CATION-INDUCED CONFORMATIONAL SWITCH WITHIN A LOOP SPANNING SEGMENT OF A DNA QUADRUPLEX CONTAINING G-G-G-C REPEATS, NMR, 8 STRUCTURES

Template:ABSTRACT PUBMED 9737927

About this Structure

Full experimental information is available from OCA.

Reference

A K cation-induced conformational switch within a loop spanning segment of a DNA quadruplex containing G-G-G-C repeats., Bouaziz S, Kettani A, Patel DJ, J Mol Biol. 1998 Sep 25;282(3):637-52. PMID:9737927

Page seeded by OCA on Mon Jun 30 16:23:59 2008

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