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| {{STRUCTURE_312d| PDB=312d | SCENE= }} | | {{STRUCTURE_312d| PDB=312d | SCENE= }} |
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| '''Z-DNA HEXAMER WITH 5' OVERHANGS THAT FORM A REVERSE WATSON-CRICK BASE PAIR'''
| | ===Z-DNA HEXAMER WITH 5' OVERHANGS THAT FORM A REVERSE WATSON-CRICK BASE PAIR=== |
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| ==Overview==
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| We have solved the structures of the homoduplex d(Gm5CGCGCG)2, and the heteroduplexes d(GCGCGCG)/d(TCGCGCG) and d(GCGCGCG)/d(CCGCGCG). The structures form six base-pairs of identical Z-DNA duplexes with single nucleotides overhanging at the 5'-ends. The overhanging nucleotide from one strand remains stacked and sandwiched between the blunt-ends of two adjacent Z-DNA duplexes, while the overhanging base of the opposing strand is extra-helical. The stacked and the extra-helical bases from adjacent duplexes pair to form a distorted d(G x G) reverse Hoogsteen base-pair in the d(Gm5CGCGCG)2 homoduplex, and d(G x T) reverse wobble and d(G x C) reverse Watson-Crick base-pairs in the d(GCGCGCG)/d(TCGCGCG) and d(GCGCGCG)/d(CCGCGCG) heteroduplexes, respectively. Interestingly, only the d(G,T) and d(G x C) base-pairs were observed in the heteroduplexes, suggesting that both the d(G x T) reverse wobble and d(G x C) reverse Watson-Crick base-pairs are more stable in this crystal environment than the d(G x G) reverse Hoogsteen base-pair. To estimate the relative stability of the three types of reverse base-pairs, crystals were grown using various mixtures of sequences and their strand compositions analyzed by mass spectrometry. The d(G x C) reverse Watson-Crick base-pair was estimated to be more stable by approximately 1.5 kcal/mol and the d(G x T) reverse wobble base-pair more stable by approximately 0.5 kcal/mol than the d(G x G) reverse Hoogsteen base-pair. The step during crystallization responsible for discriminating between the strands in the crystal is highly cooperative, suggesting that it occurs during the initial nucleating event of crystal growth.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9223642}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9223642 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9223642}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Overhanging base]] | | [[Category: Overhanging base]] |
| [[Category: Z-dna]] | | [[Category: Z-dna]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 20:15:10 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 23:27:04 2008'' |