Structures of the reduced and oxidized state of the mutant D24A of yeast thioredoxin 1: insights into the mechanism for the closing of the water cavity

1H, 15N and 13C backbone and side-chain assignments of reduced and S-nitrosated C62only mutant of human thioredoxin

Thioredoxins are ubiquitous and conserved small proteins. The redox-active site is composed of highly conserved Cys32 and Cys35. In higher eukaryotes, thioredoxin evolved to a gain of function in nitrosative control, with 3 extra cysteines, Cys62, Cys69, and Cys73. Human thioredoxin 1 (hTrx) is directly involved in cellular signal transduction through S-nitrosation. The understanding of the mechanism of S-nitrosation is essential. Here we produced a mutant of hTrx containing only Cys62 (C62only). We report the almost full 1H, 15N, and 13C chemical shift assignment of the reduced and S-nitrosated C62only. This study will help to measure the reactivity Cys62 toward S-nitrosants and the stability of S-nitrosated Cys62.

Polyamine-Based Thiols in Trypanosomatids: Evolution, Protein Structural Adaptations, and Biological Functions

SIGNIFICANCE

Major pathogenic enterobacteria and protozoan parasites from the phylum Euglenozoa, such as trypanosomatids, are endowed with glutathione (GSH)-spermidine (Sp) derivatives that play important roles in signaling and metal and thiol-redox homeostasis. For some Euglenozoa lineages, the GSH-Sp conjugates represent the main redox cosubstrates around which entire new redox systems have evolved. Several proteins underwent molecular adaptations to synthesize and utilize the new polyamine-based thiols. Recent Advances: The genomes of closely related organisms have recently been sequenced, which allows mining and analysis of gene sequences that belong to these peculiar redox systems. Similarly, the three-dimensional structures of several of these proteins have been solved, which allows for comparison with their counterparts in classical redox systems that rely on GSH/glutaredoxin and thioredoxin.

CRITICAL ISSUES

The evolutionary and structural aspects related to the emergence and use of GSH-Sp conjugates in Euglenozoa are reviewed focusing on unique structural specializations that proteins developed to use N¹,N⁸-bisglutathionylspermidine (trypanothione) as redox cosubstrate. An updated overview on the biochemical and biological significance of the major enzymatic activities is also provided.

FUTURE DIRECTIONS

A thiol-redox system strictly dependent on trypanothione is a feature unique to trypanosomatids. The physicochemical properties of the polyamine-GSH conjugates were a major driving force for structural adaptation of proteins that use these thiols as ligand and redox cofactor. In fact, the structural differences of indispensable components of this system can be exploited toward selective drug development. Future research should clarify whether additional cellular processes are regulated by the trypanothione system. Antioxid. Redox Signal. 28, 463-486.

1H, 13C and 15N chemical shift assignments of Saccharomyces cerevisiae type 1 thioredoxin in the oxidized state by solution NMR spectroscopy

Thioredoxins (Trx) are ubiquitous proteins that regulate several biochemical processes inside the cell. Trx is an important player, displaying oxidoreductase activity and helping to keep and regulate the oxidative state of the cellular environment. Trx also participates in the regulation of many cellular functions, such as DNA synthesis, protection against oxidative stress, cell cycle and signal transduction. The oxidized Trx is the target for another set of proteins, such as thioredoxin reductase (TrR), which used the reductive potential of NADPH. The oxidized state of Trx also plays important role in regulation of redox state in the cells. In this regard, the oxidized form of Trx is a putative conformer that contributes to the cellular redox environment. Here we report the chemical shift assignments (¹H, ¹³C and ¹⁵N) in solution at 15 °C. We also showed the secondary structure analysis of the oxidized form of yeast thioredoxin (yTrx1) as basis for future NMR studies of protein-target interactions and dynamics. The assignment was done at low concentration (200 µM) because it is important to keep intact the water cavity.