2AXB

Crystal Structure Analysis Of A 2-O-[2-(methoxy)ethyl]-2-thiothymidine Modified Oligodeoxynucleotide Duplex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.61 Å
  • R-Value Free: 0.202 
  • R-Value Work: 0.196 
  • R-Value Observed: 0.196 

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This is version 1.3 of the entry. See complete history


Literature

Stabilizing contributions of sulfur-modified nucleotides: crystal structure of a DNA duplex with 2'-O-[2-(methoxy)ethyl]-2-thiothymidines.

Diop-Frimpong, B.Prakash, T.P.Rajeev, K.G.Manoharan, M.Egli, M.

(2005) Nucleic Acids Res 33: 5297-5307

  • DOI: 10.1093/nar/gki823
  • Primary Citation of Related Structures:  
    2AXB

  • PubMed Abstract: 
  • Substitution of oxygen atoms by sulfur at various locations in the nucleic acid framework has led to analogs such as the DNA phosphorothioates and 4'-thio RNA. The phosphorothioates are excellent mimics of DNA, exhibit increased resistance to nuclease degradation compared with the natural counterpart, and have been widely used as first-generation antisense nucleic acid analogs for applications in vitro and in vivo ...

    Substitution of oxygen atoms by sulfur at various locations in the nucleic acid framework has led to analogs such as the DNA phosphorothioates and 4'-thio RNA. The phosphorothioates are excellent mimics of DNA, exhibit increased resistance to nuclease degradation compared with the natural counterpart, and have been widely used as first-generation antisense nucleic acid analogs for applications in vitro and in vivo. The 4'-thio RNA analog exhibits significantly enhanced RNA affinity compared with RNA, and shows potential for incorporation into siRNAs. 2-Thiouridine (s2U) and 5-methyl-2-thiouridine (m5s2U) are natural nucleotide analogs. s2U in tRNA confers greater specificity of codon-anticodon interactions by discriminating more strongly between A and G compared with U. 2-Thio modification preorganizes the ribose and 2'-deoxyribose sugars for a C3'-endo conformation, and stabilizes heteroduplexes composed of modified DNA and complementary RNA. Combination of the 2-thio and sugar 2'-O-modifications has been demonstrated to boost both thermodynamic stability and nuclease resistance. Using the 2'-O-[2-(methoxy)ethyl]-2-thiothymidine (m5s2Umoe) analog, we have investigated the consequences of the replacement of the 2-oxygen by sulfur for base-pair geometry and duplex conformation. The crystal structure of the A-form DNA duplex with sequence GCGTAT*ACGC (T* = m5s2Umoe) was determined at high resolution and compared with the structure of the corresponding duplex with T* = m5Umoe. Notable changes as a result of the incorporation of sulfur concern the base-pair parameter 'opening', an improvement of stacking in the vicinity of modified nucleotides as measured by base overlap, and a van der Waals interaction between sulfur atoms from adjacent m5s2Umoe residues in the minor groove. The structural data indicate only minor adjustments in the water structure as a result of the presence of sulfur. The observed small structural perturbations combined with the favorable consequences for pairing stability and nuclease resistance (when combined with 2'-O-modification) render 2-thiouracil-modified RNA a promising candidate for applications in RNAi.


    Organizational Affiliation

    Department of Chemical Engineering, School of Engineering, Vanderbilt University, Nashville, TN 37235, USA.



Macromolecules

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Entity ID: 1
MoleculeChainsLengthOrganismImage
5'-D(*GP*CP*GP*TP*AP*(S2M)P*AP*CP*GP*C)-3')A, B 10N/A
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.61 Å
  • R-Value Free: 0.202 
  • R-Value Work: 0.196 
  • R-Value Observed: 0.196 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 25.251α = 90
b = 45.002β = 90
c = 44.971γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
MAR345data collection
XDSdata scaling
AMoREphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2005-11-01
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-11
    Changes: Refinement description