12SN | pdb_000012sn

SARS-CoV-2 RNA-dependent RNA polymerase in complex with 4'-FlA nucleotide analogue


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.38 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

wwPDB Validation 3D Report Full Report

Validation slider image for 12SN

This is version 1.0 of the entry. See complete history

Literature

Substrate and target selectivity of 4'-fluoroadenosine against viral and host polymerases.

Walker, S.M.Loutan, A.J.Tchesnokov, E.P.Kocincova, D.Gordon, C.J.Escobedo, R.A.Jackson, N.Vogel, O.A.Morsheimer, K.Park, S.Gharpure, A.Urbano, I.Heacock, M.Cheng, Z.Pathak, K.Wolff, K.C.Huerta, L.Bakowski, M.A.Riva, L.Gupta, A.K.Yu, C.Das, K.Martinez-Sobrido, L.Basler, C.F.Davey, R.Wilson, I.A.Ward, A.B.Chanda, S.Chatterjee, A.K.Gotte, M.

(2026) bioRxiv 

  • DOI: https://doi.org/10.64898/2026.05.22.727251
  • Primary Citation Related Structures: 
    12SN

  • PubMed Abstract: 

    Developing safe and effective treatments against emerging RNA viruses is an important goal in pandemic preparedness efforts. 4'-fluorouridine (4'-FlU) is a broad-spectrum antiviral that was shown to inhibit viral RNA-dependent RNA polymerases (RdRps). Given its notable range of antiviral activity, this class of nucleoside analogs warrants further investigation. Here, we studied the antiviral activity and underlying mechanism of inhibition of 4'-fluoroadenosine (4'-FlA). Like 4'-FlU, 4'-FlA demonstrates a broad-spectrum of antiviral activity against eight prototypic viruses representing diverse families. Enzyme kinetics show that the triphosphate (4'-FlA-TP) is efficiently incorporated by viral RdRps. A cryo-EM structure of RdRp of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in complex with double-stranded RNA and the incorporated monophosphate (4'-FlA-MP) characterizes interactions at the active site. The incorporated analog elicits heterogeneous inhibition patterns in primer extension reactions. In contrast, templates with embedded 4'-FlA-MP inhibit incorporation of complementary UTP across the viral RdRps. However, incorporation of 4'-FIA-TP is not limited to viral polymerases and likewise includes human mitochondrial RNA polymerase. These results demonstrate the general potential for 4'-fluorinated nucleotides as antiviral drugs and guide the development of more selective derivatives for medical use in appropriate settings.

Macromolecule Content 

  • Total Structure Weight: 187.5 kDa 
  • Atom Count: 9,930 
  • Modeled Residue Count: 1,199 
  • Deposited Residue Count: 1,561 
  • Unique protein chains: 3
  • Unique nucleic acid chains: 2

Macromolecules


Find similar proteins by:|  3D Structure
Entity ID: 1
MoleculeChains  Sequence LengthOrganismDetailsImage
RNA-directed RNA polymerase nsp12975Severe acute respiratory syndrome coronavirus 2Mutation(s): 0 
Gene Names: rep1a-1b
EC: 2.7.7.48 (PDB Primary Data), 2.7.7.50 (PDB Primary Data)
UniProt
Find proteins for P0DTD1 (Severe acute respiratory syndrome coronavirus 2)
Explore P0DTD1 
Go to UniProtKB:  P0DTD1
Entity Groups
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0DTD1
Sequence Annotations
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Reference Sequence
Find similar proteins by:|  3D Structure
Entity ID: 2
MoleculeChains  Sequence LengthOrganismDetailsImage
Non-structural protein 8
B, D
217Severe acute respiratory syndrome coronavirus 2Mutation(s): 0 
Gene Names: rep1a-1b
UniProt
Find proteins for P0DTD1 (Severe acute respiratory syndrome coronavirus 2)
Explore P0DTD1 
Go to UniProtKB:  P0DTD1
Entity Groups
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0DTD1
Sequence Annotations
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Reference Sequence
Find similar proteins by:|  3D Structure
Entity ID: 3
MoleculeChains  Sequence LengthOrganismDetailsImage
Non-structural protein 7102Severe acute respiratory syndrome coronavirus 2Mutation(s): 0 
UniProt
Find proteins for P0DTC1 (Severe acute respiratory syndrome coronavirus 2)
Explore P0DTC1 
Go to UniProtKB:  P0DTC1
Entity Groups
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0DTC1
Sequence Annotations
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Reference Sequence
Find similar nucleic acids by:  Sequence
Entity ID: 4
MoleculeChains LengthOrganismImage
RNA (5'-R(P*GP*AP*UP*UP*AP*AP*GP*UP*UP*AP*U)-3')E [auth P]20Severe acute respiratory syndrome coronavirus 2
Sequence Annotations
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Reference Sequence
Find similar nucleic acids by:  (by identity cutoff) 
Entity ID: 5
MoleculeChains LengthOrganismImage
RNA (5'-R(P*UP*AP*UP*AP*AP*CP*UP*UP*AP*AP*UP*C)-3')F [auth T]30Severe acute respiratory syndrome coronavirus 2
Sequence Annotations
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Reference Sequence

Small Molecules

Ligands 4 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
A1DCZ(
Subject of Investigation/LOI)

Query on A1DCZ



Download:Ideal Coordinates CCD File
J [auth A][(2S,3S,4R,5R)-5-(4-amino-7H-pyrrolo[2,3-d]pyrimidin-7-yl)-2-fluoro-3,4-dihydroxyoxolan-2-yl]methyl dihydrogen phosphate
C11 H14 F N4 O7 P
HLGBNZPYXFQXAX-LRMGWDNHSA-N
POP
(Subject of Investigation/LOI)

Query on POP



Download:Ideal Coordinates CCD File
I [auth A]PYROPHOSPHATE 2-
H2 O7 P2
XPPKVPWEQAFLFU-UHFFFAOYSA-L
ZN
(Subject of Investigation/LOI)

Query on ZN



Download:Ideal Coordinates CCD File
G [auth A],
H [auth A]
ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
MG
(Subject of Investigation/LOI)

Query on MG



Download:Ideal Coordinates CCD File
K [auth A]MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.38 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 
EM Software:
TaskSoftware PackageVersion
MODEL REFINEMENTPHENIX1.21.1_5286
RECONSTRUCTIONcryoSPARC

Structure Validation

View Full Validation Report



Entry History 

& Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)United StatesU19 AI171443

Revision History  (Full details and data files)

  • Version 1.0: 2026-06-24
    Type: Initial release