9SHQ | pdb_00009shq

Cryo-EM structure of the endogeneous MIWI in complex with pachytene piRNA at 4.2A

• PDB DOI: https://doi.org/10.2210/pdb9SHQ/pdb
• NAKB: 9SHQ
• EM Map EMD-54908: EMDB EMDataResource

• Classification: RNA BINDING PROTEIN
• Organism(s): Mus musculus
• Mutation(s): No 


• Deposited: 2025-08-27 Released: 2026-01-21 
• Deposition Author(s): Raad, N.G., Fernandez-Rodriguez, C., Pandey, R.R., Mohammed, I., Uchikawa, E., Burger, F., Homolka, D., Pillai, R.S.
• Funding Organization(s): Swiss National Science Foundation, Other private

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Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 4.20 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

Literature

Structure of the MIWI endoribonuclease bound to pachytene piRNAs from mouse testes.

Raad, N., Fernandez-Rodriguez, C., Pandey, R.R., Mohammed, I., Uchikawa, E., Burger, F., Homolka, D., Pillai, R.S.

(2026) Cell Rep 45: 116804-116804

• PubMed: 41528842 
• DOI: https://doi.org/10.1016/j.celrep.2025.116804
• Primary Citation Related Structures: 
  9S0Z, 9S1E, 9SHP, 9SHQ


• PubMed Abstract: 
  

  PIWI-interacting RNAs (piRNAs) guide PIWI endoribonucleases to destroy transposon transcripts, ensuring animal fertility. Here, we report the cryo-electron microscopy structure of the MIWI-pachytene piRNA complex isolated from mouse testes. The piRNA is held via non-specific charge-based interactions with the RNA backbone and by specific recognition of the first nucleotide uridine by residues within the MID and PIWI domains. The first six nucleotides of the guide RNA take up the A-form conformation to facilitate pairing with the target. The RNA channel is wider than that observed in insect PIWI proteins, explaining the tolerance for piRNA seed:target mismatches. The PIWI endonuclease domain is in an inactive "un-plugged" state, with the loop containing a catalytic residue (E671) requiring structural re-orientation for activity. Furthermore, the PIWI domain reveals a conserved pre-formed pocket that may serve to accommodate a conserved tryptophan from the interacting factor GTSF1 to promote small RNA-guided endoribonuclease activity.

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Organizational Affiliation: 
• Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 1211, Switzerland. Electronic address: [e-mail].
Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 1211, Switzerland. Electronic address: [e-mail].
Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 1211, Switzerland.
Dubochet Center for Imaging Lausanne, Lausanne 1015, Switzerland.
Department of Molecular Biology, Science III, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 1211, Switzerland. Electronic address: [e-mail].

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors and generated by (software)

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 101.54 kDa 
• Atom Count: 5,409 
• Modeled Residue Count: 667 
• Deposited Residue Count: 876 
• Unique protein chains: 1
• Unique nucleic acid chains: 2

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Piwi-like protein 1	A [auth B]	870	Mus musculus	Mutation(s): 0  EC: 3.1.26
UniProt
Find proteins for Q9JMB7 (Mus musculus) Explore Q9JMB7  Go to UniProtKB:  Q9JMB7

Entity ID: 2
Molecule	Chains	Length	Organism	Image
RNA (5'-R(P*UP*UP*A)-3')	B [auth C]	3	Mus musculus

Entity ID: 3
Molecule	Chains	Length	Organism	Image
RNA (5'-R(P*CP*UP*C)-3')	C [auth D]	3	Mus musculus

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
MG (Subject of Investigation/LOI)	D [auth B]	MAGNESIUM ION Mg JLVVSXFLKOJNIY-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 4.20 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

EM Software:

Task	Software Package	Version
MODEL REFINEMENT	PHENIX	1.20.1_4487
RECONSTRUCTION	cryoSPARC

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-01-21 
Deposition Author(s): Raad, N.G., Fernandez-Rodriguez, C., Pandey, R.R., Mohammed, I., Uchikawa, E., Burger, F., Homolka, D., Pillai, R.S.

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Funding Organization	Location	Grant Number
Swiss National Science Foundation	Switzerland	310030_215346
Swiss National Science Foundation	Switzerland	#51NF40-205601
Other private		The Lalor Foundation

Revision History  

• Version 1.0: 2026-01-21
  Type: Initial release