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Slade D.,University of Paris Descartes | Radman M.,University of Paris Descartes | Radman M.,Mediterranean Institute for Life Sciences
Microbiology and Molecular Biology Reviews | Year: 2011

Deinococcus radiodurans is a robust bacterium best known for its capacity to repair massive DNA damage efficiently and accurately. It is extremely resistant to many DNA-damaging agents, including ionizing radiation and UV radiation (100 to 295 nm), desiccation, and mitomycin C, which induce oxidative damage not only to DNA but also to all cellular macromolecules via the production of reactive oxygen species. The extreme resilience of D. radiodurans to oxidative stress is imparted synergistically by an efficient protection of proteins against oxidative stress and an efficient DNA repair mechanism, enhanced by functional redundancies in both systems. D. radiodurans assets for the prevention of and recovery from oxidative stress are extensively reviewed here. Radiation- and desiccation-resistant bacteria such as D. radiodurans have substantially lower protein oxidation levels than do sensitive bacteria but have similar yields of DNA double-strand breaks. These findings challenge the concept of DNA as the primary target of radiation toxicity while advancing protein damage, and the protection of proteins against oxidative damage, as a new paradigm of radiation toxicity and survival. The protection of DNA repair and other proteins against oxidative damage is imparted by enzymatic and nonenzymatic antioxidant defense systems dominated by divalent manganese complexes. Given that oxidative stress caused by the accumulation of reactive oxygen species is associated with aging and cancer, a comprehensive outlook on D. radiodurans strategies of combating oxidative stress may open new avenues for antiaging and anticancer treatments. The study of the antioxidation protection in D. radiodurans is therefore of considerable potential interest for medicine and public health. Copyright © 2011, American Society for Microbiology. All Rights Reserved.

The proteome of the radiation- and desiccation-resistant bacterium D. radiodurans features a group of proteins that contain significant intrinsically disordered regions that are not present in non-extremophile homologues. Interestingly, this group includes a number of housekeeping and repair proteins such as DNA polymerase III, nudix hydrolase and rotamase. Here, we focus on a member of the nudix hydrolase family from D. radiodurans possessing low-complexity N- and C-terminal tails, which exhibit sequence signatures of intrinsic disorder and have unknown function. The enzyme catalyzes the hydrolysis of oxidatively damaged and mutagenic nucleotides, and it is thought to play an important role in D. radiodurans during the recovery phase after exposure to ionizing radiation or desiccation. We use molecular dynamics simulations to study the dynamics of the protein, and study its hydration free energy using the GB/SA formalism. We show that the presence of disordered tails significantly decreases the hydration free energy of the whole protein. We hypothesize that the tails increase the chances of the protein to be located in the remaining water patches in the desiccated cell, where it is protected from the desiccation effects and can function normally. We extrapolate this to other intrinsically disordered regions in proteins, and propose a novel function for them: intrinsically disordered regions increase the "surface-properties" of the folded domains they are attached to, making them on the whole more hydrophilic and potentially influencing, in this way, their localization and cellular activity.

Kuzmanic A.,Mediterranean Institute for Life Sciences | Zagrovic B.,University of Split
Biophysical Journal | Year: 2010

Root mean-square deviation (RMSD) after roto-translational least-squares fitting is a measure of global structural similarity of macromolecules used commonly. On the other hand, experimental x-ray B-factors are used frequently to study local structural heterogeneity and dynamics in macromolecules by providing direct information about root mean-square fluctuations (RMSF) that can also be calculated from molecular dynamics simulations. We provide a mathematical derivation showing that, given a set of conservative assumptions, a root mean-square ensemble-average of an all-against-all distribution of pairwise RMSD for a single molecular species, 〈RMSD2〉 1/2, is directly related to average B-factors (〈B〉) and 〈RMSF2〉1/2. We show this relationship and explore its limits of validity on a heterogeneous ensemble of structures taken from molecular dynamics simulations of villin headpiece generated using distributed-computing techniques and the Folding@Home cluster. Our results provide a basis for quantifying global structural diversity of macromolecules in crystals directly from x-ray experiments, and we show this on a large set of structures taken from the Protein Data Bank. In particular, we show that the ensemble-average pairwise backbone RMSD for a microscopic ensemble underlying a typical protein x-ray structure is ∼1.1 Å , under the assumption that the principal contribution to experimental B-factors is conformational variability. © 2010 by the Biophysical Society.

Krisko A.,Mediterranean Institute for Life Sciences | Radman M.,Mediterranean Institute for Life Sciences | Radman M.,French Institute of Health and Medical Research
Cold Spring Harbor Perspectives in Biology | Year: 2013

The bacterium Deinococcus radiodurans is a champion of extreme radiation resistance that is accounted for by a highly efficient protection against proteome, but not genome, damage. A well-protected functional proteome ensures cell recovery from extensive radiation damage to other cellular constituents by molecular repair and turnover processes, including an efficient repair of disintegrated DNA. Therefore, cell death correlates with radiationinduced protein damage, rather than DNA damage, in both robust and standard species. From the reviewed biology of resistance to radiation and other sources of oxidative damage, we conclude that the impact of protein damage on the maintenance of life has been largely underestimated in biology and medicine. © 2013 Cold Spring Harbor Laboratory Press; all rights reserved.

Krisko A.,Mediterranean Institute for Life Sciences | Radman M.,Mediterranean Institute for Life Sciences | Radman M.,French Institute of Health and Medical Research
PLoS Genetics | Year: 2013

Although the genome contains all the information necessary for maintenance and perpetuation of life, it is the proteome that repairs, duplicates and expresses the genome and actually performs most cellular functions. Here we reveal strong phenotypes of physiological oxidative proteome damage at the functional and genomic levels. Genome-wide mutations rates and biosynthetic capacity were monitored in real time, in single Escherichia coli cells with identical levels of reactive oxygen species and oxidative DNA damage, but with different levels of irreversible oxidative proteome damage (carbonylation). Increased protein carbonylation correlates with a mutator phenotype, whereas reducing it below wild type level produces an anti-mutator phenotype identifying proteome damage as the leading cause of spontaneous mutations. Proteome oxidation elevates also UV-light induced mutagenesis and impairs cellular biosynthesis. In conclusion, protein damage reduces the efficacy and precision of vital cellular processes resulting in high mutation rates and functional degeneracy akin to cellular aging. © 2013 Krisko, Radman.

Radman M.,Mediterranean Institute for Life Sciences | Radman M.,University of Paris Descartes
DNA Repair | Year: 2016

This paper promotes a concept that protein damage determines radiation resistance and underlies aging and age-related diseases. The first bottleneck in cell recovery from radiation damage is functional (proteome) rather than informational (DNA), since prokaryotic and eukaryotic cell death correlates with incurred protein, but not DNA, damage. Proteome protection against oxidative damage determines survival after ionizing or UV irradiation, since sufficient residual proteome activity is required to turn on the DNA damage response activating DNA repair and protein renewal processes.Extreme radiation and desiccation resistance of rare bacterial and animal species is accounted for by exceptional constitutive proteome protection against oxidative damage. After excessive radiation their well-protected proteome faithfully reconstitutes a transcription-competent genome from hundreds of DNA fragments. The observation that oxidative damage targeted selectively to cellular proteins results in aging-like phenotypes suggests that aging and age-related diseases could be phenotypic consequences of proteome damage patterns progressing with age. © 2016 Elsevier B.V.

Elez M.,University of Paris Descartes | Radman M.,University of Paris Descartes | Radman M.,Mediterranean Institute for Life Sciences | Matic I.,University of Paris Descartes
Nucleic Acids Research | Year: 2012

Mismatch repair (MMR) is an evolutionarily conserved DNA repair system, which corrects mismatched bases arising during DNA replication. MutS recognizes and binds base pair mismatches, while the MutL protein interacts with MutS-mismatch complex and triggers MutH endonuclease activity at a distal-strand discrimination site on the DNA. The mechanism of communication between these two distal sites on the DNA is not known. We used functional fluorescent MMR proteins, MutS and MutL, in order to investigate the formation of the fluorescent MMR protein complexes on mismatches in real-time in growing Escherichia coli cells. We found that MutS and MutL proteins co-localize on unrepaired mismatches to form fluorescent foci. MutL foci were, on average, 2.7 times more intense than the MutS foci co-localized on individual mismatches. A steric block on the DNA provided by the MutHE56A mutant protein, which binds to but does not cut the DNA at the strand discrimination site, decreased MutL foci fluorescence 3-fold. This indicates that MutL accumulates from the mismatch site toward strand discrimination site along the DNA. Our results corroborate the hypothesis postulating that MutL accumulation assures the coordination of the MMR activities between the mismatch and the strand discrimination site. © 2012 The Author(s).

Petrov D.,University of Vienna | Petrov D.,Mediterranean Institute for Life Sciences | Petrov D.,University of Split | Zagrovic B.,University of Vienna | And 2 more authors.
Journal of the American Chemical Society | Year: 2011

One of the most important irreversible oxidative modifications of proteins is carbonylation, the process of introducing a carbonyl group in reaction with reactive oxygen species. Notably, carbonylation increases with the age of cells and is associated with the formation of intracellular protein aggregates and the pathogenesis of age-related disorders such as neurodegenerative diseases and cancer. However, it is still largely unclear how carbonylation affects protein structure, dynamics, and aggregability at the atomic level. Here, we use classical molecular dynamics simulations to study structure and dynamics of the carbonylated headpiece domain of villin, a key actin-organizing protein. We perform an exhaustive set of molecular dynamics simulations of a native villin headpiece together with every possible combination of carbonylated versions of its seven lysine, arginine, and proline residues, quantitatively the most important carbonylable amino acids. Surprisingly, our results suggest that high levels of carbonylation, far above those associated with cell death in vivo, may be required to destabilize and unfold protein structure through the disruption of specific stabilizing elements, such as salt bridges or proline kinks, or tampering with the hydrophobic effect. On the other hand, by using thermodynamic integration and molecular hydrophobicity potential approaches, we quantitatively show that carbonylation of hydrophilic lysine and arginine residues is equivalent to introducing hydrophobic, charge-neutral mutations in their place, and, by comparison with experimental results, we demonstrate that this by itself significantly increases the intrinsic aggregation propensity of both structured, native proteins and their unfolded states. Finally, our results provide a foundation for a novel experimental strategy to study the effects of carbonylation on protein structure, dynamics, and aggregability using site-directed mutagenesis. © 2011 American Chemical Society.

Mediterranean Institute for Life Sciences | Date: 2013-12-18

Vaccines and therapeutic proteins, including polyclonal and monoclonal antibodies, must be maximally pure and stable in their most active native form. This is a requirement for their maximal efficacy, specificity and stability as well as for precluding immune responses against erroneous or damaged moieties. Similar considerations hold for proteins used in diagnostics, industry and research. The most frequent source of damage to proteins produced in living cells is the diverse product of oxidative damage. Two main sources of protein oxidation are the level of reactive oxygen species (ROS) and even more importantly the intrinsic susceptibility of proteins to oxidative damage. Methods for avoiding oxidative protein damage are disclosed, including providing for (i) a decrease in intracellular ROS levels and (ii) an increase in the intrinsic resilience of proteins to oxidative damage. Metabolites synthesized by the most robust species provide exceptionally high levels of protection against oxidative damage from ROS. High fidelity ribosomal mutations and over-expression of diverse chaperones increase the accuracy of protein biosynthesis and of protein post-synthetic folding, both greatly contributing to increased intrinsic resistance of proteins to oxidative damage.

Mediterranean Institute for Life Sciences | Date: 2014-02-15

The process of aging and the development of age-related diseases are related to the emerging phenotypes of increasingly damaged and progressively malfunctioning proteomes. The present invention provides methods of preventing aging and age-related diseases in mammals by assessment of protein-specific oxidative damage. Methods of providing treatments that reduce intracellular reactive oxygen and/or nitrogen species, or protein-specific damage caused by reactive oxygen and/or nitrogen species, are disclosed. Furthermore, methods of screening for compounds that reduce intracellular reactive oxidative species, and/or molecules that prevent protein-specific damage by protecting the susceptible protein from such damage and therefore prevent or treat degenerative or age-related diseases, are also disclosed.

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