scholarly journals Intracellular catalysis of disulfide bond formation by the human sulfhydryl oxidase, QSOX1

2007 ◽  
Vol 404 (3) ◽  
pp. 403-411 ◽  
Author(s):  
Seema Chakravarthi ◽  
Catherine E. Jessop ◽  
Martin Willer ◽  
Colin J. Stirling ◽  
Neil J. Bulleid
Keyword(s):  
Disulfide Bond ◽  
Mammalian Cells ◽  
Transmembrane Protein ◽  
Bond Formation ◽  
Secretory Protein ◽  
Lung Fibroblasts ◽  
Carboxypeptidase Y ◽  
Disulfide Bond Formation ◽  
Endometrial Cells

The discovery that the flavoprotein oxidase, Erv2p, provides oxidizing potential for disulfide bond formation in yeast, has led to investigations into the roles of the mammalian homologues of this protein. Mammalian homologues of Erv2p include QSOX (sulfhydryl oxidases) from human lung fibroblasts, guinea-pig endometrial cells and rat seminal vesicles. In the present study we show that, when expressed in mammalian cells, the longer version of human QSOX1 protein (hQSOX1a) is a transmembrane protein localized primarily to the Golgi apparatus. We also present the first evidence showing that hQSOX1a can act in vivo as an oxidase. Overexpression of hQSOX1a suppresses the lethality of a complete deletion of ERO1 (endoplasmic reticulum oxidase 1) in yeast and restores disulfide bond formation, as assayed by the folding of the secretory protein carboxypeptidase Y.

Production of H2O2 in the Endoplasmic Reticulum Promotes In Vivo Disulfide Bond Formation

2012 ◽  
Vol 16 (10) ◽  
pp. 1088-1099 ◽  
Author(s):  
Éva Margittai ◽  
Péter Löw ◽  
Ibolya Stiller ◽  
Alessandra Greco ◽  
Jose Manuel Garcia-Manteiga ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Disulfide Bond ◽  
Bond Formation ◽  
Disulfide Bond Formation

scholarly journals A pathway for disulfide bond formation in vivo.

1993 ◽  
Vol 90 (3) ◽  
pp. 1038-1042 ◽  
Author(s):  
J. C. Bardwell ◽  
J. O. Lee ◽  
G. Jander ◽  
N. Martin ◽  
D. Belin ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Bond Formation ◽  
Disulfide Bond Formation

Two dileucine motifs mediate late endosomal/lysosomal targeting of transmembrane protein 192 (TMEM192) and a C-terminal cysteine residue is responsible for disulfide bond formation in TMEM192 homodimers

2011 ◽  
Vol 434 (2) ◽  
pp. 219-231 ◽  
Author(s):  
Jörg Behnke ◽  
Eeva-Liisa Eskelinen ◽  
Paul Saftig ◽  
Bernd Schröder
Keyword(s):  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Transmembrane Protein ◽  
Bond Formation ◽  
Immunogold Labelling ◽  
Disulfide Bridge ◽  
Cysteine Residue ◽  
Disulfide Bond Formation ◽  
Transmembrane Segments ◽  
Late Endosomes

TMEM192 (transmembrane protein 192) is a novel constituent of late endosomal/lysosomal membranes with four potential transmembrane segments and an unknown function that was initially discovered by organellar proteomics. Subsequently, localization in late endosomes/lysosomes has been confirmed for overexpressed and endogenous TMEM192, and homodimers of TMEM192 linked by disulfide bonds have been reported. In the present study the molecular determinants of TMEM192 mediating its transport to late endosomes/lysosomes were analysed by using CD4 chimaeric constructs and mutagenesis of potential targeting motifs in TMEM192. Two directly adjacent N-terminally located dileucine motifs of the DXXLL-type were found to be critical for transport of TMEM192 to late endosomes/lysosomes. Whereas disruption of both dileucine motifs resulted in mistargeting of TMEM192 to the plasma membrane, each of the two motifs was sufficient to ensure correct targeting of TMEM192. In order to study disulfide bond formation, mutagenesis of cysteine residues was performed. Mutation of Cys266 abolished disulfide bridge formation between TMEM192 molecules, indicating that TMEM192 dimers are linked by a disulfide bridge between their C-terminal tails. According to the predicted topology, Cys266 would be localized in the reductive milieu of the cytosol where disulfide bridges are generally uncommon. Using immunogold labelling and proteinase protection assays, the localization of the N- and C-termini of TMEM192 on the cytosolic side of the late endosomal/lysosomal membrane was experimentally confirmed. These findings may imply close proximity of the C-termini in TMEM192 dimers and a possible involvement of this part of the protein in dimer assembly.

Identification of a protein required for disulfide bond formation in vivo

Cell ◽  
1991 ◽  
Vol 67 (3) ◽  
pp. 581-589 ◽  
Author(s):  
James C.A. Bardwell ◽  
Karen McGovern ◽  
Jon Beckwith
Keyword(s):  
Disulfide Bond ◽  
Bond Formation ◽  
Disulfide Bond Formation

scholarly journals Functional Analysis of Paralogous Thiol-disulfide Oxidoreductases in Streptococcus gordonii

2013 ◽  
Vol 288 (23) ◽  
pp. 16416-16429 ◽  
Author(s):  
Lauren Davey ◽  
Crystal K. W. Ng ◽  
Scott A. Halperin ◽  
Song F. Lee
Keyword(s):  
Disulfide Bond ◽  
Bond Formation ◽  
Extracellular Proteins ◽  
Extracellular Dna ◽  
Disulfide Bond Formation ◽  
Streptococcus Gordonii ◽  
Erythromycin Resistance ◽  
Gram Positive ◽  
Gram Positive Bacteria

Disulfide bonds are important for the stability of many extracellular proteins, including bacterial virulence factors. Formation of these bonds is catalyzed by thiol-disulfide oxidoreductases (TDORs). Little is known about their formation in Gram-positive bacteria, particularly among facultative anaerobic Firmicutes, such as streptococci. To investigate disulfide bond formation in Streptococcus gordonii, we identified five putative TDORs from the sequenced genome. Each of the putative TDOR genes was insertionally inactivated with an erythromycin resistance cassette, and the mutants were analyzed for autolysis, extracellular DNA release, biofilm formation, bacteriocin production, and genetic competence. This analysis revealed a single TDOR, SdbA, which exhibited a pleiotropic mutant phenotype. Using an in silico analysis approach, we identified the major autolysin AtlS as a natural substrate of SdbA and showed that SdbA is critical to the formation of a disulfide bond that is required for autolytic activity. Analysis by BLAST search revealed homologs to SdbA in other Gram-positive species. This study provides the first in vivo evidence of an oxidoreductase, SdbA, that affects multiple phenotypes in a Gram-positive bacterium. SdbA shows low sequence homology to previously identified oxidoreductases, suggesting that it may belong to a different class of enzymes. Our results demonstrate that SdbA is required for disulfide bond formation in S. gordonii and indicate that this enzyme may represent a novel type of oxidoreductase in Gram-positive bacteria.

scholarly journals Two phases of disulfide bond formation have differing requirements for oxygen

2013 ◽  
Vol 203 (4) ◽  
pp. 615-627 ◽  
Author(s):  
Marianne Koritzinsky ◽  
Fiana Levitin ◽  
Twan van den Beucken ◽  
Ryan A. Rumantir ◽  
Nicholas J. Harding ◽  
...  
Keyword(s):  
Er Stress ◽  
Disulfide Bond ◽  
Electron Acceptor ◽  
Disulfide Bonds ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Bond Formation ◽  
Disulfide Bond Formation ◽  
Terminal Electron Acceptor ◽  
Two Phases

Most proteins destined for the extracellular space require disulfide bonds for folding and stability. Disulfide bonds are introduced co- and post-translationally in endoplasmic reticulum (ER) cargo in a redox relay that requires a terminal electron acceptor. Oxygen can serve as the electron acceptor in vitro, but its role in vivo remains unknown. Hypoxia causes ER stress, suggesting a role for oxygen in protein folding. Here we demonstrate the existence of two phases of disulfide bond formation in living mammalian cells, with differential requirements for oxygen. Disulfide bonds introduced rapidly during protein synthesis can occur without oxygen, whereas those introduced during post-translational folding or isomerization are oxygen dependent. Other protein maturation processes in the secretory pathway, including ER-localized N-linked glycosylation, glycan trimming, Golgi-localized complex glycosylation, and protein transport, occur independently of oxygen availability. These results suggest that an alternative electron acceptor is available transiently during an initial phase of disulfide bond formation and that post-translational oxygen-dependent disulfide bond formation causes hypoxia-induced ER stress.

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