The Machinery for Oxidative Protein Folding in Thermophiles

Abstract

Disulfide bonds are required for the stability and function of many proteins. A large number of thiol-disulfide oxidoreductases, belonging to the thioredoxin superfamily, catalyze protein disulfide bond formation in all living cells, from bacteria to humans. The protein disulfide isomerase (PDI) is the eukaryotic factor that catalyzes oxidative protein folding in the endoplasmic reticulum; by contrast, in prokaryotes, a family of disulfide bond (Dsb) proteins have an equivalent outcome in the bacterial periplasm. Recently the results from genome analysis suggested an important role for disulfide bonds in the structural stabilization of intracellular proteins from thermophiles. A specific protein disulfide oxidoreductase (PDO) has a key role in intracellular disulfide shuffling in thermophiles. Here we focus on the structural and functional characterization of PDO correlated with the multifunctional eukaryotic PDI. In addition, we highlight the chimeric nature of the machinery for oxidative protein folding in thermophiles in comparison with the mesophilic bacterial and eukaryal counterparts.

Transcriptomes of the Extremely Thermoacidophilic Archaeon Metallosphaera sedula Exposed to Metal “Shock” Reveal Generic and Specific Metal Responses

“…As such, the induction of bcp4 (Msed_0359) by HD Co 2ϩ and by LD and HD Zn 2ϩ suggests that metal shock triggered endogenous oxidative stress. Also in S. solfataricus, PDO is the substrate of thioredoxin reductase and plays a central role in the biochemistry of cytoplasmic disulfide bonds (34). Exposure to HD Co 2ϩ , Cu 2ϩ , and Zn 2ϩ induced PDO in M. sedula, implying that these metals impacted disulfide bonds and/or their formation.…”

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

“…Disulfide bond formation is catalyzed by thioredoxin-like proteins in non-reducing compartments like the eukaryotic endoplasmic reticulum, the inner membrane space of mitochondria, and the periplasm of Gram-negative bacteria (13). The protein-disulfide isomerase was the first disulfide bondforming enzyme discovered by Anfinsen and colleagues (14,15) that contains two redox-active CXXC motifs.…”

Redox Biology: Computational Approaches to the Investigation of Functional Cysteine Residues

“…Structural Cys are often used in secreted proteins and those located in oxidizing environments, such as bacterial periplasm and eukaryotic endoplasmic reticulum (ER), but are much less frequent in reducing environments (e.g., cytosol, nucleus and mitochondrial matrix). However, in some thermophilic bacteria, structure stabilization through disulfide bonds is used even for cytosolic proteins (75). Many computational and experimental studies revealed that disulfide bridges can increase conformational stability of proteins, mainly by reducing the conformational entropy of the unfolded state and constraining the unfolded conformation (1,5,85).…”