Identification and characterization of a selenoprotein family containing a diselenide bond in a redox motif

Abstract

Selenocysteine (Sec, U) insertion into proteins is directed by translational recoding of specific UGA codons located upstream of a stem-loop structure known as Sec insertion sequence (SECIS) element. Selenoproteins with known functions are oxidoreductases containing a single redox-active Sec in their active sites. In this work, we identified a family of selenoproteins, designated SelL, containing two Sec separated by two other residues to form a UxxU motif. SelL proteins show an unusual occurrence, being present in diverse aquatic organisms, including fish, invertebrates, and marine bacteria. Both eukaryotic and bacterial SelL genes use single SECIS elements for insertion of two Sec. In eukaryotes, the SECIS is located in the 3 UTR, whereas the bacterial SelL SECIS is within a coding region and positioned at a distance that supports the insertion of either of the two Sec or both of these residues. SelL proteins possess a thioredoxin-like fold wherein the UxxU motif corresponds to the catalytic CxxC motif in thioredoxins, suggesting a redox function of SelL proteins. Distantly related SelL-like proteins were also identified in a variety of organisms that had either one or both Sec replaced with Cys. Danio rerio SelL, transiently expressed in mammalian cells, incorporated two Sec and localized to the cytosol. In these cells, it occurred in an oxidized form and was not reducible by DTT. In a bacterial expression system, we directly demonstrated the formation of a diselenide bond between the two Sec, establishing it as the first diselenide bond found in a natural protein.oxidoreductase ͉ selenocysteine ͉ thioredoxin-like fold

Key metabolic pathways involved in xenobiotic biotransformation and stress responses revealed by transcriptomics of the mangrove oyster Crassostrea brasiliana

“…A number of contigs encoding genes putatively involved in the antioxidative system were identified in the C. brasiliana transcriptome with the thioredoxin-related contigs most represented (Table 6). Thioredoxin-related enzymes are involved in thiol-based redox regulation and belong to the thioredoxin (Trx) superfamily, which also consists of glutathione peroxidase, peroxiredoxin and glutaredoxin gene family members (Shchedrina et al, 2007). The activities of these enzymes have been proposed to protect against metal exposure and virus-induced oxidative stress in molluscs (Nikapitiya et al, 2009;Trevisan et al, 2011;, although none were significantly up-regulated in response to the treatments applied here.…”

Selenoprotein K Binds Multiprotein Complexes and Is Involved in the Regulation of Endoplasmic Reticulum Homeostasis

“…The proteins were detected using Pierce silver stain kit (Thermo Scientific) according to the manufacturer's recommendations. SDS-PAGE was performed as previously described (37). The proteins were detected using Coomassie Brilliant Blue Staining or silver staining (Pierce) according to the manufacturer's recommendations.…”

“…The proteins were detected using Coomassie Brilliant Blue Staining or silver staining (Pierce) according to the manufacturer's recommendations. Western blotting was performed as previously described (37). Dilution of antibodies was used according to the manufacturer's recommendations.…”

“…Bound proteins were eluted with denaturing 1ϫ SDS-PAGE sample buffer (Invitrogen) by boiling for 5 min. The 75 Se radioactivity pattern was detected using a PhosphorImager system (GE Healthcare) as described (37).…”

Bioinformatic prediction of selenoprotein genes in the dolphin genome

“…Multiple alignments of DI2 show that both of them have local sequence conservation ( Figure 5). There are very rare selenoproteins (SelP and SelL) that have 2 or more than 2 Sec residues [16,17]. More Sec residues mean higher redox activity, and further work could be done based on this protein to investigate the relationship between function and numbers of Sec residues in selenoproteins.…”