ATP and Mg2+ promote the reversible oligomerization and aggregation of chloroplast 2-Cys peroxiredoxin

Hierarchical peroxiredoxin assembly through orthogonal pH-response and electrostatic interactions

Morpheeins are proteins that adapt their morphology and function to the environment. Therefore, their use in nanotechnology opens up the bottom-up preparation of anisotropic metamaterials, based on the sequential use of different stimuli. A prominent member of this family of proteins is peroxiredoxins (Prx), with dual peroxidase and chaperone function, depending on the pH of the media. At high pH, they show a toroidal morphology that turns into tubular stacks upon acidification. While the toroidal conformers have been explored as building blocks to yield 1D and 2D structures, the obtention of higher ordered materials remain unexplored. In this research, the morpheein behaviour of Prx is exploited to yield columnar aggregates, that are subsequently self-assembled into 3D anisotropic bundles. This is achieved by electrostatic recognition between the negatively charged protein rim and a positively charged porphyrin acting as molecular glue. The subsequent and orthogonal input lead to the alignment of the monodimensional stacks side-by-side, leading to the precise assembly of this anisotropic materials.

Elucidation of the Binding Mechanism of Anionic Phospholipids to Antioxidant Protein Peroxiredoxin 2

Peroxiredoxins (Prxs) belong to a family of ubiquitously expressed peroxidases that detoxify reactive oxygen species. In addition to their enzymatic function, Prxs also function as molecular chaperones. This functional switch is related to their degree of oligomerization. We have previously revealed that Prx2 interacts with anionic phospholipids and that the anionic phospholipid-containing Prx2 oligomer forms a high molecular weight (HMW) complex in a nucleotide-dependent manner. However, the detailed mechanism of the oligomer and HMW complex formation remains unclear. In this study, we investigated the anionic phospholipid binding site in Prx2 using site-directed mutagenesis to understand the mechanism of the oligomer formation. Our findings demonstrated that six binding site residues in Prx2 are important for the binding of anionic phospholipids.

Negatively Charged Lipids Are Essential for Functional and Structural Switch of Human 2-Cys Peroxiredoxin II

The function of ubiquitous 2-Cys peroxiredoxins (Prxs) can be converted alternatively from peroxidases to molecular chaperones. This conversion has been reported to occur by the formation of high-molecular-weight (HMW) complexes upon overoxidation of or ATP/ADP binding to 2-Cys Prxs, but its mechanism is not well understood. Here, we show that upon binding to phosphatidylserine or phosphatidylglycerol dimeric human 2-Cys PrxII (hPrxII) is assembled to trefoil-shaped small oligomers (possibly hexamers) with full chaperone and null peroxidase activities. Spherical HMW complexes are formed, only when phosphatidylserine or phosphatidylglycerol is bound to overoxidized or ATP/ADP-bound hPrxII. The spherical HMW complexes are lipid vesicles covered with trefoil-shaped oligomers arranged in a hexagonal lattice pattern. Thus, these lipids with a net negative charge, which can be supplied by increased membrane trafficking under oxidative stress, are essential for the structural and functional switch of hPrxII and possibly most 2-Cys Prxs.

Characterization of CNL like protein fragment (CNL-LPF) from mature Lageneria siceraria seeds

Coiled coil domain-nucleotide binding site-leucine rich repeat (CC-NBS-LRR; CNL) proteins are highly conserved family of plant disease resistance proteins, remarkably comprise of coiled-coil domain, which plays significant role in plant innate immunity. The present study reports that moderately elicited oligomerization of plant CNL like protein fragment (CNL-LPF) in presence of ATP/Mg using various biophysical methods Circular dichroism (CD) results depicted a substantial increase in β-sheet structure content of CNL-LPF. ATP/Mg induced conformational change in protein was observed by increase in blue shift with extrinsic fluorescence measurement, which indicates the exposure of hydrophobic regions of CNL-LPF and leads to self-association i.e. oligomerization. Likewise, cluster of protein oligomer and alteration in protein surface morphology were observed in presence of ATP/Mg by Transmission electron microscopy (TEM) and Atomic force microscopy (AFM), respectively. Also, augmented antiproliferation of HT1376 cells (urinary bladder cancer cell lines) was observed by CNL-LPF in presence of ATP/Mg. In conclusion, the current study illustrates that extent of CNL-LPF oligomerization was enhanced in presence of ATP/Mg (as compared to its absence). Utilization of enhanced oligomerization property of CNL-LPF as an anti-proliferative agent needs more assessment.

Peroxiredoxins in parasites

SIGNIFICANCE

Parasite survival and virulence relies on effective defenses against reactive oxygen and nitrogen species produced by the host immune system. Peroxiredoxins (Prxs) are ubiquitous enzymes now thought to be central to such defenses and, as such, have potential value as drug targets and vaccine antigens.

RECENT ADVANCES

Plasmodial and kinetoplastid Prx systems are the most extensively studied, yet remain inadequately understood. For many other parasites our knowledge is even less well developed. Through parasite genome sequencing efforts, however, the key players are being discovered and characterized. Here we describe what is known about the biochemistry, regulation, and cell biology of Prxs in parasitic protozoa, helminths, and fungi. At least one Prx is found in each parasite with a sequenced genome, and a notable theme is the common patterns of expression, localization, and functionality among sequence-similar Prxs in related species.

CRITICAL ISSUES

The nomenclature of Prxs from parasites is in a state of disarray, causing confusion and making comparative inferences difficult. Here we introduce a systematic Prx naming convention that is consistent between organisms and informative about structural and evolutionary relationships.

FUTURE DIRECTIONS

The new nomenclature should stimulate the crossfertilization of ideas among parasitologists and with the broader redox research community. The diverse parasite developmental stages and host environments present complex systems in which to explore the variety of roles played by Prxs, with a view toward parlaying what is learned into novel therapies and vaccines that are urgently needed.

The C-terminal extension of chloroplast 2-Cys peroxiredoxin is critical for interaction with ATP

2-Cys peroxiredoxins (2-Cys Prxs) are ubiquitous enzymes that have been implicated in peroxide-mediated signaling of markedly different processes, such as cancer and photosynthesis. A highly conserved C-terminal extension of eukaryotic homologues modulates both the overoxidation of cysteines and the formation of oligomers. Here, we reveal that the plant counterpart regulates the self-polymerization of 2-Cys Prx triggered by ATP and Mg(2+). This feature is of particular importance under oxidative stress because the interaction of ATP with 2-Cys Prx rapidly integrates nonredox chemistry of signaling pathways into a network hub governed by multiple redox transformations at cysteine residues.