PDBsum entry 4z7x

Oxidoreductase

PDB id: 4z7x

Contents

Protein chains

211 a.a.

Ligands

3CX ×2

Waters ×451

PDB id:

4z7x

Name:

Oxidoreductase

Title:

Mdba protein, a thiol-disulfide oxidoreductase from actinomyces oris.

Structure:

Mdba. Chain: a, b. Engineered: yes

Source:

Actinomyces oris. Organism_taxid: 544580. Gene: mdba, ana_1994. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

1.55Å R-factor: 0.127 R-free: 0.180

Authors:

J.Osipiuk,M.E.Reardon-Robinson,H.Ton-That,A.Joachimiak,Midwest Center For Structural Genomics (Mcsg)

Key ref:

M.E.Reardon-Robinson et al. (2015). A Disulfide Bond-forming Machine Is Linked to the Sortase-mediated Pilus Assembly Pathway in the Gram-positive Bacterium Actinomyces oris. J Biol Chem, 290, 21393-21405. PubMed id: 26170452 DOI: 10.1074/jbc.M115.672253

Date:

08-Apr-15 Release date: 22-Apr-15

Protein chains

A0A0M3KL32  (A0A0M3KL32_9ACTO) -  MdbA from Actinomyces oris

Seq: 238 a.a.

Struc: 211 a.a.

DOI no: 10.1074/jbc.M115.672253

J Biol Chem 290:21393-21405 (2015)

PubMed id: 26170452

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

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

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.