Molecular and Functional Characterization of Thioredoxin 1 from Korean Rose Bitterling (Rhodeus uyekii)

Molecular and functional characterization of unique thermo-halophilic thioredoxin from the metagenome of an exotic environment

The lower convective layer (LCL) at Atlantis II brine pool of the Red sea represents one of the exceptional, unique ecosystems. Thioredoxin is a multi-functional antioxidant redox protein that has a crucial role in various vital cellular processes. In the current study, a functional metagenomics approach was used to isolate and characterize thioredoxin from the LCL of Atlantis II Deep brine pool (Trx-ATII). From the metagenomic DNA of the LCL, the thioredoxin gene was directly retrieved and sequenced. Sequence analysis showed that the gene belonged to thioredoxin-like superfamily with classical Trx motif (-CXXC-). Phylogenetic analysis revealed that Trx-ATII was closely related to Trx of Prochlorococcus marinus with a maximum identity of 86%. Successfully, Trx-ATII was cloned and expressed in E. coli, where the purified protein had M.wt of 16 kDa. Characterization studies revealed that Trx-ATII protein is halophilic; can tolerate up to 2.5 M NaCl and thermostable, where 90% of its activity was retained at 60 °C. Trx-ATII can reduce both DTNB and insulin disulfide- containing substrates. In conclusion, a unique thioredoxin protein was isolated from a harsh environment that can maintain its activity under extreme conditions of salinity and temperature as a promising redox protein for biotechnological applications.

Unusual AT-skew of Sinorhodeus microlepis mitogenome provides new insights into mitogenome features and phylogenetic implications of bitterling fishes

Sinorhodeus microlepis (S. microlepis) is recently described as a new species and represents a new genus Sinorhodeu of the subfamily Acheilognathinae. In this study, we first sequenced the complete mitogenome of S. microlepis and compared with the other 29 bitterling mitogenomes. The S. microlepis mitogenome is 16,591 bp in length and contains 37 genes. Gene distribution pattern is identical among 30 bitterling mitogenomes. A significant linear correlation between A+T% and AT-skew were found among 29 bitterling mitogenomes, except S. microlepis shows unusual AT-skew with slightly negative in tRNAs and PCGs. Bitterling mitogenomes exhibit highly conserved usage bias of start codon, relative synonymous codons and amino acids, overlaps and non-coding intergenic spacers. Phylogenetic trees constructed by 13 PCGs strongly support the polyphyly of the genus Acheilognathus and the paraphyly of Rhodeus and Tanakia. Together with the unusual characters of S. microlepis mitogenomes and phylogenetic trees, S. microlepis should be a sister species to the genus Rhodeu that might diverge about 13.69 Ma (95% HPD: 12.96-14.48 Ma).

Molecular characterization of Rhodeus uyekii tripartite motif protein 1 (TRIM1) involved in IFN-γ/LPS-induced NF-κB signaling

The tripartite motif-containing (TRIM) proteins are involved in a wide range of cellular processes, and the role of TRIM1 in immunity has been explored. However, fundamental studies on fish TRIM1 are lacking. In this study, we cloned and characterized TRIM1 cDNA from the Korean rose bitterling, Rhodeus uyekii (RuTRIM1). Two RuTRIM1 isoforms (RuTRIM1-X1 and RuTRIM1-X2) were identified. The coding sequence (CDS) of RuTRIM1-X1 comprised 2157 bp encoding a 718-aa protein, and the CDS of RuTRIM1-X2 comprised 1929 bp encoding a 642-aa protein. Both RuTRIM1 isoforms contained a RING finger domain, B-box 1, B-box 2, coiled-coil domain, COS box, FN3 motif, and PRY/SPRY domain. The deduced RuTRIM1-X1 and RuTRIM1-X2 proteins had high amino acid identity (76.27-98.89%) with orthologs from various other species, and a phylogenetic tree was constructed. RuTRIM1-X1 and RuTRIM1-X2 mRNA were expressed in all tissues examined, with the highest expression levels detected in the hepatopancreas. During early development, RuTRIM1-X1 and RuTRIM1-X2 mRNA levels changed differently from the gastrula period to the first feeding stage. An in vivo ubiquitination assay showed that RuTRIM1 exhibited RING-dependent E3 ubiquitin ligase activity, mainly by comparing RuTRIM1-X2 to RuTRIM1-X1. The subcellular localization of the two RuTRIM1 protein isoforms was characterized, revealing that they formed aggregates in cytoplasmic bodies in Raw264.7 cells. Interferon-γ/lipopolysaccharide-induced nuclear factor-κB signaling was negatively regulated by RuTRIM1-X1 and RuTRIM1-X2, and the negative effect was reversed in RING deletion mutants. To our knowledge, this is the first study to characterize fish TRIM1, which may play a role in the inflammatory response.

Cloning and functional characterization of thioredoxin genes from large yellow croaker Larimichthys crocea

Thioredoxin(Trx)with a redox-active disulfide/dithiol in the active site, is an ubiquitous disulfide reductase majorly responsible for maintaining the balance of reactive oxygen species. In this study, the complete thioredoxin-like protein 1 (designated as LcTrx) was cloned from large yellow croaker Larimichthys crocea through rapid amplification of cDNA ends. The full-length cDNA of LcTrx was 1295 bp in length containing a 131 bp 5' untranslated region (UTR) ,a 3'UTR of 294bp with a poly (A) tail, and an 870 bp open reading frame (ORF) encoding a polypeptide of 289 amino acids. Protein sequence analysis revealed that LcTrx contains the evolutionarily conserved redox motif CRPC (Cys-Arg-Pro-Cys-). Multiple alignments revealed that LcTrx is highly identical to Trx from other organisms, especially in the CRPC motifs. The recombinant LcTrx showed obvious insulin reduction activity in vitro. The LcTrx transcripts were constitutively expressed in all examined tissues with the highest levels found in the muscles and the lowest in the head kidney. Results of Vibrio parahaemolyticus infection experiment showed that the expression levels of LcTrx were tissue and time dependent. In the liver and kidney, LcTrx was down-regulated both at 12 h and 48 h post-infection. In contrast, LcTrx showed induced expression in the spleen and head kidney at same post-infection time points. The different responses to pathogen stimulation indicated the diversified physiological function of LcTrx in the four examined tissues.

The Interactions between ZnO Nanoparticles (NPs) and α-Linolenic Acid (LNA) Complexed to BSA Did Not Influence the Toxicity of ZnO NPs on HepG2 Cells

Background: Nanoparticles (NPs) entering the biological environment could interact with biomolecules, but little is known about the interaction between unsaturated fatty acids (UFA) and NPs. Methods: This study used α-linolenic acid (LNA) complexed to bovine serum albumin (BSA) for UFA and HepG2 cells for hepatocytes. The interactions between BSA or LNA and ZnO NPs were studied. Results: The presence of BSA or LNA affected the hydrodynamic size, zeta potential, UV-Vis, fluorescence, and synchronous fluorescence spectra of ZnO NPs, which indicated an interaction between BSA or LNA and NPs. Exposure to ZnO NPs with the presence of BSA significantly induced the damage to mitochondria and lysosomes in HepG2 cells, associated with an increase of intracellular Zn ions, but not intracellular superoxide. Paradoxically, the release of inflammatory cytokine interleukin-6 (IL-6) was decreased, which indicated the anti-inflammatory effects of ZnO NPs when BSA was present. The presence of LNA did not significantly affect all of these endpoints in HepG2 cells exposed to ZnO NPs and BSA. Conclusions: the results from the present study indicated that BSA-complexed LNA might modestly interact with ZnO NPs, but did not significantly affect ZnO NPs and BSA-induced biological effects in HepG2 cells.

Comparative analysis of two thioredoxin-like genes in black rockfish Sebastes schlegelii and their possible involvement in redox homeostasis and innate immune responses

Elevated levels of ROS can cause serious intracellular damages by reacting readily with nucleic acids, proteins and lipids, thus triggering tissue damage and cell death. Thioredoxin system is one of the principal factors that maintain the intracellular redox balance via its antioxidant property. In this study, we characterized two new thioredoxin isoforms (SsTXN-like 1 and SsMtTXN-like) from black rockfish, Sebastes schlegelii. The molecular and structural characteristics, as well as the evolutionary relationships of SsTXN-like 1 and SsMtTXN-like confirmed that they belong to the thioredoxin superfamily. A classical thioredoxin domain was found in both proteins with a conserved redox-active site CXYC, however, only the precursor of SsMtTXN-like protein possessed a mitochondrial targeting signal. The results from insulin disulfide reduction activity assay demonstrated that their recombinant proteins are capable of reducing the disulfide bonds of oxidatively damaged proteins via their oxidoreductase activities. The free radical scavenging activity assay revealed the prominent hydroxyl and DPPH scavenging activities of rSsTXN-like 1 and rSsMtTXN-like in a dose-dependent manner. Transcriptional studies showed a broad distribution of SsTXN-like 1 and SsMtTXN-like transcripts in all the examined tissues. Significant (p < 0.05) up-regulations of both genes in immune-related tissues after LPS, poly I:C and Streptococcus iniae challenges reflect their critical role in redox homeostasis in black rockfish. Taken together, SsTXN-like 1 and SsMtTXN-like, as two active members of thioredoxin superfamily, have significant antioxidant properties to housekeep the redox potential during various stress conditions and innate immune response of Sebastes schlegelii.