9Z6I | pdb_00009z6i

Cryo-EM structure of the open state of cIL RNA at 4.3 A resolution

  • Classification: RNA
  • Organism(s): synthetic construct
  • Mutation(s): No 

  • Deposited: 2025-11-14 Released: 2026-05-27 
  • Deposition Author(s): Filippova, E.V., Kossiakoff, A.A.
  • Funding Organization(s): National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)

Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 4.32 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

Starting Model: experimental
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wwPDB Validation 3D Report Full Report

Validation slider image for 9Z6I

This is version 1.1 of the entry. See complete history

Literature

A universal Fab targeting a conserved U1A-RNA epitope for RNA structure determination by cryo-EM.

Filippova, E.V.Krochmal, D.Mukherjee, S.Piccirilli, J.A.Kossiakoff, A.A.

(2026) Nucleic Acids Res 54

  • DOI: https://doi.org/10.1093/nar/gkag502
  • Primary Citation Related Structures: 
    9YXV, 9Z6I

  • PubMed Abstract: 

    Recent advances in cryo-electron microscopy (cryo-EM) have made antigen-binding fragments (Fabs) essential tools in the field of structural biology. Fabs facilitate image alignment, thereby enhancing three-dimensional (3D) reconstruction, and increase the effective size of proteins, aiding in their structural elucidation. In this study, we sought to broaden the use of Fabs as fiducial markers to elucidate the structures of RNA molecules. Identifying an appropriate Fab for a specific RNA target can be particularly challenging due to RNA's inherent flexibility and tendency to assume multiple conformations, which complicate the process and prolong the structure determination timeline. To address this challenge, we designed a universal Fab that specifically recognizes a U1A-RNA epitope, thereby reducing the need for Fab selection tailored to each individual RNA target. We determined the cryo-EM structure of the class I ligase ribozyme complexed with a portable U1hpII loop bound to the U1A protein and the Fab. The resulting structure revealed that the Fab interacts with a conserved U1A-RNA binding region, which can be engineered into other RNA molecules. This strategy presents significant potential for streamlining the structural determination of various RNAs, which are essential for biological and biomedical research.


  • Organizational Affiliation
    • Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, United States.

Macromolecule Content 

  • Total Structure Weight: 49.84 kDa 
  • Atom Count: 2,644 
  • Modeled Residue Count: 124 
  • Deposited Residue Count: 155 
  • Unique nucleic acid chains: 1

Macromolecules

Find similar nucleic acids by:  (by identity cutoff) 
Entity ID: 1
MoleculeChains LengthOrganismImage
RNA (155-MER)155synthetic construct
Sequence Annotations
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Reference Sequence

Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 4.32 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 
EM Software:
TaskSoftware PackageVersion
MODEL REFINEMENTPHENIX1.20.1_4487
RECONSTRUCTIONcryoSPARC3.3.1

Structure Validation

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Entry History 

& Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United States--

Revision History  (Full details and data files)

  • Version 1.0: 2026-05-27
    Type: Initial release
  • Version 1.1: 2026-06-03
    Changes: Data collection, Database references