3BBI

Minimally Junctioned Hairpin Ribozyme Incorporating A38(2AP) and A-1 2'-O-Me Modifications near Active Site


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.228 
  • R-Value Observed: 0.228 

Starting Model: experimental
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This is version 1.2 of the entry. See complete history


Literature

Structural effects of nucleobase variations at key active site residue Ade38 in the hairpin ribozyme.

MacElrevey, C.Salter, J.D.Krucinska, J.Wedekind, J.E.

(2008) RNA 14: 1600-1616

  • DOI: https://doi.org/10.1261/rna.1055308
  • Primary Citation of Related Structures:  
    3B58, 3B5A, 3B5F, 3B5S, 3B91, 3BBI, 3BBK, 3BBM, 3CR1

  • PubMed Abstract: 

    The hairpin ribozyme requires functional groups from Ade38 to achieve efficient bond cleavage or ligation. To identify molecular features that contribute to catalysis, structures of position 38 base variants 2,6-diaminopurine (DAP), 2-aminopurine (AP), cytosine (Cyt), and guanine (Gua) were determined between 2.2 and 2.8 A resolution. For each variant, two substrate modifications were compared: (1) a 2'-O-methyl-substituent at Ade-1 was used in lieu of the nucleophile to mimic the precatalytic state, and (2) a 3'-deoxy-2',5'-phosphodiester linkage between Ade-1 and Gua+1 was used to mimic a reaction-intermediate conformation. While the global fold of each variant remained intact, the results revealed the importance of Ade38 N1 and N6 groups. Absence of N6 resulting from AP38 coincided with failure to localize the precatalytic scissile phosphate. Cyt38 severely impaired catalysis in a prior study, and its structures here indicated an anti base conformation that sequesters the imino moiety from the scissile bond. Gua38 was shown to be even more deleterious to activity. Although the precatalytic structure was nominally affected, the reaction-intermediate conformation indicated a severe electrostatic clash between the Gua38 keto oxygen and the pro-Rp oxygen of the scissile bond. Overall, position 38 modifications solved in the presence of 2'-OMe Ade-1 deviated from in-line geometry, whereas variants with a 2',5' linkage exhibited S-turn destabilization, as well as base conformational changes from syn to anti. These findings demonstrate the importance of the Ade38 Watson-Crick face in attaining a reaction-intermediate state and the sensitivity of the RNA fold to restructuring when electrostatic and shape features fail to complement.


  • Organizational Affiliation

    Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.


Macromolecules

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Entity ID: 1
MoleculeChains LengthOrganismImage
Loop A Substrate strand13N/A
Sequence Annotations
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  • Reference Sequence
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Entity ID: 2
MoleculeChains LengthOrganismImage
Loop A and Loop B Ribozyme strand30N/A
Sequence Annotations
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  • Reference Sequence

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Entity ID: 3
MoleculeChains LengthOrganismImage
Loop B S-turn strand19N/A
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.228 
  • R-Value Observed: 0.228 
  • Space Group: P 61 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 93.25α = 90
b = 93.25β = 90
c = 132.83γ = 120
Software Package:
Software NamePurpose
CrystalCleardata collection
CNSrefinement
CrystalCleardata reduction
CrystalCleardata scaling
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-08-12
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 1.2: 2023-08-30
    Changes: Data collection, Database references, Derived calculations, Refinement description