5ana
From Proteopedia
(New page: 200px<br /> <applet load="5ana" size="450" color="white" frame="true" align="right" spinBox="true" caption="5ana, resolution 2.250Å" /> '''THE CRYSTAL STRUCT...) |
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caption="5ana, resolution 2.250Å" /> | caption="5ana, resolution 2.250Å" /> | ||
'''THE CRYSTAL STRUCTURE OF D(GTACGTAC) AT 2.25 ANGSTROMS RESOLUTION. ARE THE A-DNA'S ALWAYS UNWOUND APPROXIMATELY 10 DEGREES AT THE C-G STEPS'''<br /> | '''THE CRYSTAL STRUCTURE OF D(GTACGTAC) AT 2.25 ANGSTROMS RESOLUTION. ARE THE A-DNA'S ALWAYS UNWOUND APPROXIMATELY 10 DEGREES AT THE C-G STEPS'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The structure of the self-complementary octamer d(GTACGTAC) has been | + | The structure of the self-complementary octamer d(GTACGTAC) has been analyzed by a single crystal X-ray diffraction method at 2.25 A resolution. The crystallographic R factor was 0.184 for all 1233 reflections at this resolution. In spite of the alternating purine-pyrimidine sequence, d(GTACGTAC) adopts the A-form conformation rather than the left-handed Z-form. The average helix twist and the mean rise per base pair are 32.1 degrees and 3.18 A, respectively. The d(GTACGTAC) helix is characterized by a wide open major groove and small base-pair tilt (9.7 degrees). The partial unwinding of the helix is observed only at the central pyrimidine-purine C-G step, but not at the other pyrimidine-purine T-A steps. Based on this study and six other X-ray studies, we propose a hypothesis that the A-DNA's are always unwound approximately 10 degrees at the C-G steps. Significant differences in base-pair stacking modes are seen between the purine-pyrimidine step and the pyrimidine-purine step. All deoxyribose rings adopt the C3'-endo conformation. All backbone torsion angles fall into the range expected for the A-DNA form, except for the nucleotide G5, whose alpha and gamma torsion angles adopt the trans, trans conformation instead of the common gauche-, gauche+ conformation. |
==About this Structure== | ==About this Structure== | ||
| - | 5ANA is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with MG as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 5ANA is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with <scene name='pdbligand=MG:'>MG</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5ANA OCA]. |
==Reference== | ==Reference== | ||
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[[Category: double helix]] | [[Category: double helix]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 19:14:50 2008'' |
Revision as of 17:14, 21 February 2008
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THE CRYSTAL STRUCTURE OF D(GTACGTAC) AT 2.25 ANGSTROMS RESOLUTION. ARE THE A-DNA'S ALWAYS UNWOUND APPROXIMATELY 10 DEGREES AT THE C-G STEPS
Overview
The structure of the self-complementary octamer d(GTACGTAC) has been analyzed by a single crystal X-ray diffraction method at 2.25 A resolution. The crystallographic R factor was 0.184 for all 1233 reflections at this resolution. In spite of the alternating purine-pyrimidine sequence, d(GTACGTAC) adopts the A-form conformation rather than the left-handed Z-form. The average helix twist and the mean rise per base pair are 32.1 degrees and 3.18 A, respectively. The d(GTACGTAC) helix is characterized by a wide open major groove and small base-pair tilt (9.7 degrees). The partial unwinding of the helix is observed only at the central pyrimidine-purine C-G step, but not at the other pyrimidine-purine T-A steps. Based on this study and six other X-ray studies, we propose a hypothesis that the A-DNA's are always unwound approximately 10 degrees at the C-G steps. Significant differences in base-pair stacking modes are seen between the purine-pyrimidine step and the pyrimidine-purine step. All deoxyribose rings adopt the C3'-endo conformation. All backbone torsion angles fall into the range expected for the A-DNA form, except for the nucleotide G5, whose alpha and gamma torsion angles adopt the trans, trans conformation instead of the common gauche-, gauche+ conformation.
About this Structure
5ANA is a Protein complex structure of sequences from [1] with as ligand. Full crystallographic information is available from OCA.
Reference
The crystal structure of d(GTACGTAC) at 2.25 A resolution: are the A-DNA's always unwound approximately 10 degrees at the C-G steps?, Takusagawa F, J Biomol Struct Dyn. 1990 Feb;7(4):795-809. PMID:2310515
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