Abstract
Methionine sulfoxide reductases are found in all domains of life and are important in reversing the oxidative damage of the free and protein forms of methionine, a sulfur containing amino acid particularly sensitive to reactive oxygen species (ROS). Archaea are microbes of a domain of life distinct from bacteria and eukaryotes. Archaea are well known for their ability to withstand harsh environmental conditions that range from habitats of high ROS, such as hypersaline lakes of intense ultraviolet (UV) radiation and desiccation, to hydrothermal vents of low concentrations of dissolved oxygen at high temperature. Recent evidence reveals the methionine sulfoxide reductases of archaea function not only in the reduction of methionine sulfoxide but also in the ubiquitin-like modification of protein targets during oxidative stress, an association that appears evolutionarily conserved in eukaryotes. Here is reviewed methionine sulfoxide reductases and their distribution and function in archaea.
Highlights
Reactive oxygen species (ROS), such as singlet oxygen (1 O2 ), hydrogen peroxide (H2 O2 ), superoxide anion (O− 2 ) and hydroxyl radical (HO), can cause widespread damage to cells
The archaeal methionine sulfoxide reductase (MSR) enzymes are of particular interest in terms of evolutionary history [25,28,29] and how protein homeostasis is maintained in extreme habitats [26], as these enzymes are recently linked to ubiquitin-like protein modification pathways that are associated with oxidative stress and sulfur mobilization [32]
The MSR homologs of archaea include: (i) MSRA and MSRB, which are prevalent in archaea but notably absent from mostthermophiles, (ii) fRMSR and MSRP, which are noted in archaea but are not common, and (iii) molybdopterin (MPT)/tungstopterin (WPT) oxidoreductase (OR) enzymes of the sulfite oxidase and DMSO reductase families (e.g., DMSO reductase, formate dehydrogenase, assimilatory nitrate reductase and formylmethanofuran dehydrogenase), which are widespread in archaea but are not known to function in MetO reduction [33,34,35,36] (Table S1)
Summary
Reactive oxygen species (ROS), such as singlet oxygen (1 O2 ), hydrogen peroxide (H2 O2 ), superoxide anion (O− 2 ) and hydroxyl radical (HO), can cause widespread damage to cells. MSRP of the molybdopterin-dependent sulfite oxidase family reduces free and protein forms of Met-R-O and Met-S-O [13,14] and can reduce dimethylsulfoxide (DMSO), trimethylamine-N-oxide (TMAO) and phenylmethyl sulfoxide in vitro [15]. Members of the molybdopterin-dependent DMSO reductase family, such as BisC [16,17], DmsA [18], TorZ/MSRZ [19] and BisZ [20], reduce free and/or protein forms of MetO in addition to other substrates such as biotin sulfoxide, nicotinamide-N-oxide, adenosine-N-oxide, DMSO and/or TMAO. The inter- and intra-disulfide bonds are reduced by thiol relay systems systemsUltimately, such as nicotinamide adenine dinucleotide (phosphate) hydrogen [NAD(P)H]such dependent as nicotinamide adenine dinucleotide [NAD(P)H]-dependent thioredoxin thioredoxin reductase (TrxR)/thioredoxin (Trx) or glutathione reductase (GR)/glutathione reductase (TrxR)/thioredoxin (Trx) or[21] This reduction recycles the MSR enzyme (GSH)/glutaredoxin back to an active (Grx)state. B-type heme transmembrane protein of the NADPH oxidase family [13,14], which shuttles electrons from the quinone pool [13,14]
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