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The misfolding and mutation of Cu/Zn superoxide dismutase (SOD1) is commonly associated with amyotrophic lateral sclerosis (ALS). SOD1 can accumulate within stress granules (SGs), a type of membraneless organelle, which is believed to form via liquid–liquid phase separation (LLPS). Using wild‐type, metal‐deficient, and different ALS disease mutants of SOD1 and computer simulations, we report here that the absence of Zn leads to structural disorder within two loop regions of SOD1, triggering SOD1 LLPS and amyloid formation. The addition of exogenous Zn to either metal‐free SOD1 or to the severe ALS mutation I113T leads to the stabilization of the loops and impairs SOD1 LLPS and aggregation. Moreover, partial Zn‐mediated inhibition of LLPS was observed for another severe ALS mutant, G85R, which shows perturbed Zn‐binding. By contrast, the ALS mutant G37R, which shows reduced Cu‐binding, does not undergo LLPS. In addition, SOD1 condensates induced by Zn‐depletion exhibit greater cellular toxicity than aggregates formed by prolonged incubation under aggregating conditions. Overall, our work establishes a role for Zn‐dependent modulation of SOD1 conformation and LLPS properties that may contribute to amyloid formation. Synopsis: The formation of membraneless organelles, such as stress granules (SGs), is believed to occur through the process of liquid–liquid phase separation (LLPS). The amyotrophic lateral sclerosis (ALS) disease‐associated protein SOD1 is known to accumulate within SGs, but if it itself undergoes LLPS, and if this affects amyloid formation, is not well‐studied. The apo form of SOD1 undergoes LLPS.SOD1 LLPS and subsequent aggregation are regulated by a conformational transition between a disordered and a relatively compact folded state.The metal cofactor Zn prevents SOD1 LLPS via a conformational transition.SOD1 condensates show greater cytotoxicity than aggregates. [ABSTRACT FROM AUTHOR]

The sole existence of a t-bone-shaped naphthalimide derivative [2-(2-aminoethyl)-1 H-benzo[de]isoquinoline-1,3(2 H)dione] (NAP), which gives rise to a photoinduced electron transfer (PET) mechanism, has been established using a combination of experimental and theoretical studies. In parallel an in vitro-in cell PET mechanism has also been shown. To understand the photophysics of NAP, solvent studies have been carried out in different solvents. In addition, theoretical calculations have been conducted to explain the spectroscopic properties through optimized structures. A 'turn off' PET mechanism has also been observed in the presence of specific metal ions, namely, Cr3+, Fe3+ and Hg2+ among a series of metal ions. Theoretical studies reveal that NAP-Cr3+, NAP-Fe3+ and NAP-Hg2+ have their HOMO energy states lying in between a HOMO-LUMO energy state of the t-bone-type NAP molecule. On the contrary, the HOMO state of the other metal ion-NAP conjugate (NAP-M n+) does not lie in between the HOMO-LUMO energy gap of the t-bone-type NAP molecule. Coupled with in vitro studies, in cell investigations reveal an enhancement of fluorescence intensity of NAP upon cytosolic metal sensing. Furthermore, a very high cell viability of NAP treated cells as tested by MTT assay and a fast permeation of the said compound as revealed by flow cytometry suggest NAP to be a potential candidate in metal sensing and bioimaging applications. [ABSTRACT FROM AUTHOR]

Trehalose-6-phosphate phosphatase (TPP) catalyzes the final step in the biosynthesis of the anti-stress sugar trehalose. An 82 kDa TPP enzyme was isolated from Candida utilis with 61% yield and 43-fold purification. The protein sequence, determined by N-terminal sequencing and MALDI-TOF analysis, showed significant homology with known TPP sequences from related organisms. The full length gene sequence of TPP of C. utilis was identified using rapid amplification of cDNA ends-PCR reaction (RACE-PCR). The gene was cloned and expressed in Escherichia coli BL21. Recombinant TPP enzyme was isolated using affinity chromatography. CD spectroscopy and steady-state fluorescence revealed that the structural and conformational aspects were identical in both native and recombinant forms. The biochemical properties of the two forms were also similar. Km was determined to be ~0.8 mM. Optimum temperature and pH were found to be 30 °C and 8.5, respectively. Activity was dependent on the presence of divalent cations and inhibited by metal chelators. Methylation-mediated regulation of TPP enzyme and its effect on the overall survival of the organism under stress were investigated. The results indicated that enhancement of TPP activity by methylation at the Cysteine residues increased resistance of Candida cells against thermal stress. This work involves extensive investigations toward understanding the physico-chemical properties of the first TPP enzyme from any yeast strain. The mechanism by which methylation regulates its activity has also been studied. A correlation between regulation of trehalose synthesis and survivability of the organism under thermal stress was established. J. Cell. Physiol. 229: 1245-1255, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The presence of magnetic nanoparticles (NPs) in physiological systems induces toxicity through its effects on mitochondrial function and reactive oxygen species (ROS) imbalance. Magnetic NP induced cytotoxicity has been elaborately evaluated for impending threats, however, a detailed investigation is lacking. It is shown that the interaction of Fe3O4 NPs with cytochrome c can lead to different events based on the NPs to protein ratio, the solution conditions, and the type of surface protection. At low NPs concentration, rapid binding and subsequent electron transfer are the preferred events while at higher concentration slow oxidative modification of the protein is initiated. The slow event of protein modification yields conformational disorientation, loss of stability, and formation of amyloid-like structures with cytochrome c. The possibility that the NP induced oxidative stress and age can work in concert to compromise different aspects of cellular quality control processes is discussed. Suitable surface modifications of the NPs inhibit their direct binding to the protein molecules and minimize NP induced toxicity. [ABSTRACT FROM AUTHOR]

The image shows the major findings of Goutam De, Krishnananda Chattopadhyay, and coworkers, who studied the interaction between iron oxide nanoparticles and cytochrome c, as reported on page 683. The triangle at the top left shows the binding of the protein onto the surface of the bare particles forming amyloid fibrils (transmission electron microscopy image is shown in the background). Appropriate surface modification inhibits protein binding and amyloid formation (shown in the triangle at the bottom right). [ABSTRACT FROM AUTHOR]