MdbA protein, a thiol-disulfide oxidoreductase from Actinomyces oris.

Experimental Data Snapshot

  • Resolution: 1.55 Å
  • R-Value Free: 0.180 
  • R-Value Work: 0.124 
  • R-Value Observed: 0.127 

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Ligand Structure Quality Assessment 

This is version 1.3 of the entry. See complete history


A Disulfide Bond-forming Machine Is Linked to the Sortase-mediated Pilus Assembly Pathway in the Gram-positive Bacterium Actinomyces oris.

Reardon-Robinson, M.E.Osipiuk, J.Chang, C.Wu, C.Jooya, N.Joachimiak, A.Das, A.Ton-That, H.

(2015) J Biol Chem 290: 21393-21405

  • DOI: https://doi.org/10.1074/jbc.M115.672253
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Export of cell surface pilins in Gram-positive bacteria likely occurs by the translocation of unfolded precursor polypeptides; however, how the unfolded pilins gain their native conformation is presently unknown. Here, we present physiological studies to demonstrate that the FimA pilin of Actinomyces oris contains two disulfide bonds. Alanine substitution of cysteine residues forming the C-terminal disulfide bridge abrogates pilus assembly, in turn eliminating biofilm formation and polymicrobial interaction. Transposon mutagenesis of A. oris yielded a mutant defective in adherence to Streptococcus oralis, and revealed the essential role of a vitamin K epoxide reductase (VKOR) gene in pilus assembly. Targeted deletion of vkor results in the same defects, which are rescued by ectopic expression of VKOR, but not a mutant containing an alanine substitution in its conserved CXXC motif. Depletion of mdbA, which encodes a membrane-bound thiol-disulfide oxidoreductase, abrogates pilus assembly and alters cell morphology. Remarkably, overexpression of MdbA or a counterpart from Corynebacterium diphtheriae, rescues the Δvkor mutant. By alkylation assays, we demonstrate that VKOR is required for MdbA reoxidation. Furthermore, crystallographic studies reveal that A. oris MdbA harbors a thioredoxin-like fold with the conserved CXXC active site. Consistently, each MdbA enzyme catalyzes proper disulfide bond formation within FimA in vitro that requires the catalytic CXXC motif. Because the majority of signal peptide-containing proteins encoded by A. oris possess multiple Cys residues, we propose that MdbA and VKOR constitute a major folding machine for the secretome of this organism. This oxidative protein folding pathway may be a common feature in Actinobacteria.

  • Organizational Affiliation

    From the Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
238Actinomyces orisMutation(s): 0 
Gene Names: mdbAANA_1994
Find proteins for A0A0M3KL32 (Actinomyces oris)
Explore A0A0M3KL32 
Go to UniProtKB:  A0A0M3KL32
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA0A0M3KL32
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on 3CX

Download Ideal Coordinates CCD File 
C [auth A],
D [auth B]
(2S)-3-(cyclohexylamino)-2-hydroxypropane-1-sulfonic acid
C9 H19 N O4 S
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
A, B
Experimental Data & Validation

Experimental Data

  • Resolution: 1.55 Å
  • R-Value Free: 0.180 
  • R-Value Work: 0.124 
  • R-Value Observed: 0.127 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 46.88α = 90
b = 66.86β = 90
c = 256.169γ = 90
Software Package:
Software NamePurpose
HKL-3000data scaling
PDB_EXTRACTdata extraction
HKL-3000data reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesGM094585
National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR)United StatesDE017382
National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR)United StatesDE025015

Revision History  (Full details and data files)

  • Version 1.0: 2015-04-22
    Type: Initial release
  • Version 1.1: 2015-09-09
    Changes: Database references
  • Version 1.2: 2017-09-20
    Changes: Author supporting evidence, Database references, Derived calculations
  • Version 1.3: 2019-12-11
    Changes: Author supporting evidence