44NR | pdb_000044nr

Crystal structure of a BME-trapped intermediate-like form of mouse MsrA

• PDB DOI: https://doi.org/10.2210/pdb44NR/pdb

• Classification: OXIDOREDUCTASE
• Organism(s): Mus musculus
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2026-08-05 Released: 2026-10-28 
• Deposition Author(s): Shin, B.M., Hawkes, H.-J.K., Park, S.H., Ki, H.S., Kim, S.H., Shah, F., Di Trapani, G., Tonissen, K.F., Hwang, K.Y.
• Funding Organization(s): National Research Foundation (NRF, Korea)

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.62 Å
• R-Value Free: 
  0.181 (Depositor), 0.180 (DCC) 
• R-Value Work: 
  0.158 (Depositor), 0.158 (DCC) 
• R-Value Observed: 
  0.160 (Depositor) 

Starting Model: experimental

Literature

Structural basis for cysteine-linked redox-state plasticity in mammalian methionine sulfoxide reductase A.

Shin, B., Hawkes, H.K., Park, S., Ki, H., Kim, S., Shah, F., Di Trapani, G., Tonissen, K.F., Hwang, K.Y.

(2026) Redox Biol 97: 104436-104436

• PubMed: 42860110 
• DOI: https://doi.org/10.1016/j.redox.2026.104436
• Primary Citation Related Structures: 
  44ND, 44NI, 44NR


• PubMed Abstract: 
  

  Methionine sulfoxide reductase A (MsrA) protects proteins from oxidative damage through cysteine-based redox cycling, but how mammalian MsrA is structurally regulated during oxidation and reductive recycling has remained unclear. We report three crystal structures of mouse MsrA (mMsrA) that capture distinct redox states - reduced (3.0 Å), BME-trapped intermediate-like (BTIL; 1.6 Å), and oxidized (1.9 Å) - and reveal an unrecognized layer of regulation centered on Cys107. The BTIL structure visualizes catalytic Cys72 as a mixed disulfide with β-mercaptoethanol (BME) alongside a sulfenic acid at Cys107, a configuration not previously observed. The oxidized structure resolves the canonical Cys72-Cys218 disulfide together with an unexpected Cys107-Cys227 pairing that locks a C-terminal loop into a cap over the active site. LC-MS/MS mapping, MD simulations, activity assays, and thioredoxin (Trx)-trapping experiments converge on a model in which Cys72 drives catalysis, while Cys107-mediated disulfide rearrangement and Cys227-directed Trx entry gate substrate access and enzymatic regeneration - defining a noncanonical oxidized state that expands the mechanistic repertoire of mammalian MsrA under oxidative stress.

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Organizational Affiliation: 
• Department of Biotechnology, College of Life Sciences & Biotechnology, Korea University, Seoul, 02841, Republic of Korea.
Intercollege, Hanyang University, Seoul, 04763, Republic of Korea; School of Environment and Science, Griffith University, Brisbane, QLD, 4111, Australia.
School of Environment and Science, Griffith University, Brisbane, QLD, 4111, Australia.
School of Environment and Science, Griffith University, Brisbane, QLD, 4111, Australia; Institute for Biomedicine and Glycomics, Griffith University, Brisbane, QLD, 4111, Australia. Electronic address: [e-mail].
Department of Biotechnology, College of Life Sciences & Biotechnology, Korea University, Seoul, 02841, Republic of Korea. Electronic address: [e-mail].

Biological Assembly 1  

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

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

Biological Assembly Evidence: gel filtration

Macromolecule Content 

• Total Structure Weight: 26.21 kDa 
• Atom Count: 1,859 
• Modeled Residue Count: 191 
• Deposited Residue Count: 233 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Mitochondrial peptide methionine sulfoxide reductase	A	233	Mus musculus	Mutation(s): 0  Gene Names: Msra EC: 1.8.4.11
UniProt
Find proteins for Q9D6Y7 (Mus musculus) Explore Q9D6Y7  Go to UniProtKB:  Q9D6Y7

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
GOL	B [auth A]	GLYCEROL C3 H8 O3 PEDCQBHIVMGVHV-UHFFFAOYSA-N

Modified Residues  2 Unique
ID	Chains	Modified Residue	Modification Type	Formula	2D Diagram
CME	A	CYS	Beta-mercaptoethanol	C5 H11 N O3 S2
CSO	A	CYS	Hydroxylation	C3 H7 N O3 S

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.62 Å
• R-Value Free:  0.181 (Depositor), 0.180 (DCC) 
• R-Value Work:  0.158 (Depositor), 0.158 (DCC) 
• R-Value Observed: 0.160 (Depositor) 

Space Group: C 1 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 77.825	α = 90
b = 52.634	β = 118.67
c = 70.67	γ = 90

Software Package:

Software Name	Purpose
PHENIX	refinement
HKL-2000	data scaling
HKL-2000	data reduction
PDB_EXTRACT	data extraction
PHENIX	phasing

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-10-28 
Deposition Author(s): Shin, B.M., Hawkes, H.-J.K., Park, S.H., Ki, H.S., Kim, S.H., Shah, F., Di Trapani, G., Tonissen, K.F., Hwang, K.Y.

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Funding Organization	Location	Grant Number
National Research Foundation (NRF, Korea)	Korea, Republic Of	--

Revision History  

• Version 1.0: 2026-10-28
  Type: Initial release