X-ray evidence of a native state with increased compactness populated by tryptophan-less B. licheniformis β-lactamase

β-lactamases confer antibiotic resistance, one of the most serious world-wide health problems, and are an excellent theoretical and experimental model in the study of protein structure, dynamics and evolution. Bacillus licheniformis exo-small penicillinase (ESP) is a Class-A β-lactamase with three tryptophan residues located in the protein core. Here, we report the 1.7-Å resolution X-ray structure, catalytic parameters, and thermodynamic stability of ESPΔW, an engineered mutant of ESP in which phenylalanine replaces the wild-type tryptophan residues. The structure revealed no qualitative conformational changes compared with thirteen previously reported structures of B. licheniformis β-lactamases (RMSD = 0.4-1.2 Å). However, a closer scrutiny showed that the mutations result in an overall more compact structure, with most atoms shifted toward the geometric center of the molecule. Thus, ESPΔW has a significantly smaller radius of gyration (Rg) than the other B. licheniformis β-lactamases characterized so far. Indeed, ESPΔW has the smallest Rg among 126 Class-A β-lactamases in the Protein Data Bank (PDB). Other measures of compactness, like the number of atoms in fixed volumes and the number and average of noncovalent distances, confirmed the effect. ESPΔW proves that the compactness of the native state can be enhanced by protein engineering and establishes a new lower limit to the compactness of the Class-A β-lactamase fold. As the condensation achieved by the native state is a paramount notion in protein folding, this result may contribute to a better understanding of how the sequence determines the conformational variability and thermodynamic stability of a given fold.Fil: Risso, Valeria Alejandra. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Acierno, Juan Pablo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Capaldi, Stefano. Universita di Verona; ItaliaFil: Monaco, Hugo L.. Universita di Verona; ItaliaFil: Ermacora, Mario Roberto. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Espresso Coffee Mitigates the Aggregation and Condensation of Alzheimer′s Associated Tau Protein

: Espresso coffee is among the most consumed beverages in the world. Recent studies report a protective activity of the coffee beverage against neurodegenerative disorders such as Alzheimer's disease. Alzheimer's disease belongs to a group of disorders, called tauopathies, which are characterized by the intraneuronal accumulation of the microtubule-associated protein tau in fibrillar aggregates. In this work, we characterized by NMR the molecular composition of the espresso coffee extract and identified its main components. We then demonstrated with in vitro and in cell experiments that the whole coffee extract, caffeine, and genistein have biological properties in preventing aggregation, condensation, and seeding activity of the repeat region of tau. We also identified a set of coffee compounds capable of binding to preformed tau fibrils. These results add insights into the neuroprotective potential of espresso coffee and suggest candidate molecular scaffolds for designing therapies targeting monomeric or fibrillized forms of tau

Molecular Mechanisms of Light Harvesting in the Minor Antenna {CP}29 in Near-Native Membrane Lipidic Environment

CP29, a chlorophyll a/b-xanthophyll binding protein, bridges energy transfer between the major LHCII antenna complexes and photosystem II reaction centers. It hosts one of the two identified quenching sites, making it crucial for regulated photoprotection mechanisms. Until now, the photophysics of CP29 has been studied on the purified protein in detergent solutions since spectrally overlapping signals affect in vivo measurements. However, the protein in detergent assumes non-native conformations compared to its physiological state in the thylakoid membrane. Here, we report a detailed photophysical study on CP29 inserted in discoidal lipid bilayers, known as nanodiscs, which mimic the native membrane environment. Using picosecond time-resolved fluorescence and femtosecond transient absorption (TA), we observed shortening of the Chl fluorescence lifetime with a decrease of the carotenoid triplet formation yield for CP29 in nanodiscs as compared to the protein in detergent. Global analysis of TA data suggests a (1)Chl* quenching mechanism dependent on excitation energy transfer to a carotenoid dark state, likely the proposed S*, which is believed to be formed due to a carotenoid conformational change affecting the S-1 state. We suggest that the accessibility of the S* state in different local environments plays a key role in determining the quenching of Chl excited states. In vivo, non-photochemical quenching is activated by de-epoxidation of violaxanthin into zeaxanthin. CP29-zeaxanthin in nanodiscs further shortens the Chl lifetime, which underlines the critical role of zeaxanthin in modulating photoprotection activity.Published under an exclusive license by AIP Publishing

The crystal structure of sterol carrier protein 2 from Yarrowia lipolytica and the evolutionary conservation of a large, non-specific lipid-binding cavity

Sterol carrier protein 2 (SCP2), a small intracellular domain present in all forms of life, binds with high affinity a broad spectrum of lipids. Due to its involvement in the metabolism of long-chain fatty acids and cholesterol uptake, it has been the focus of intense research in mammals and insects; much less characterized are SCP2 from other eukaryotic cells and microorganisms. We report here the X-ray structure of Yarrowia lipolytica SCP2 (YLSCP2) at 2.2 Å resolution in complex with palmitic acid. This is the first fungal SCP2 structure solved, and it consists of the canonical five-stranded β-sheet covered on the internal face by a layer of five α-helices. The overall fold is conserved among the SCP2 family, however, YLSCP2 is most similar to the SCP2 domain of human MFE-2, a bifunctional enzyme acting on peroxisomal β-oxidation. We have identified the common structural elements defining the shape and volume of the large binding cavity in all species characterized. Moreover, we found that the cavity of the SCP2 domains is distinctly formed by carbon atoms, containing neither organized water nor rigid polar interactions with the ligand. These features are in contrast with those of fatty acid binding proteins, whose internal cavities are more polar and contain bound water. The results will help to design experiments to unveil the SCP2 function in very different cellular contexts and metabolic conditions.Fil: Pérez de Berti, Federico Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto Multidisciplinario de Biología Celular (i); Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Capaldi, Stefano. Universita Di Verona; ItaliaFil: Ferreyra, Raul Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto Multidisciplinario de Biología Celular (i); Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Burgardt, Noelia Ines. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Acierno, Juan Pablo. Universidad Nacional de Quilmes; ArgentinaFil: Klinke, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Monaco, Hugo L.. Universita Di Verona; ItaliaFil: Ermacora, Mario Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto Multidisciplinario de Biología Celular (i); Argentina. Universidad Nacional de Quilmes; Argentin

Scraping cytology and scanning electron microscopy in diagnosis and therapy of corneal ulcer by mycobacterium infection

Purpose: This work is aimed at demonstrating that scraping cytology and scanning electron microscopy can successfully assist in the diagnosis of nontuberculous mycobacteria infection. For this purpose, we report the use of both these techniques in the diagnosis of cornel ulcer in a previously healthy young man.Methods: Cytological samples were achieved by scraping technique on the mucosa, both sub palpebral and temporal area of the eye tarsal conjunctiva. The obtained sample was affixed to a sanded rectangular slide, stained with the Pappenheim method, washed in bidistilled water, treated in Giemsa solution, washed again and subsequently dried on a hot plate and observed with a microscope at various magnifications.Results: After a therapy based on a 500 mg clarithromycin tablet administered every 12 hours for 30 days as systemic therapy, a complete recovery of the patient from left eye inflammation was observed and SEM cytology showed that NTM colonies had disappeared.Conclusion: Conjunctival cytology scraping and SEM technologies can be therefore exploited as new tools in diagnosis and fast identification of these newly discovered mycobacteria. In fact, they have a new way for studying ocular pathology, because of the simple execution and remarkable accuracy in the diagnosis. In fact, this technique allows to gather valuable information about all pathogens expression and the cellular action involved in pathology. As a further plus, this technique provides clinicians with the opportunity to repeat the SEM cytology for monitoring patients during therapy, hence leading to evaluate the efficacy of the pharmaceutical regimen in real time

I tumori cistici del pancreas. Revisione della letteratura e proposta di un percorso diagnostico-terapeutico

In questo lavoro, gli Autori esaminano gli aspetti epidemiologici, clinici, anatomo-patologici, morfologico-strumentali e chimico-fisici propri di ogni singolo tipo di lesione cistica del pancreas e li paragonano tra di loro in maniera critica. In tal modo riescono ad individuare per ogni singola categoria le caratteristiche più salienti. Un percorso composto di quattro gruppi principali di esami strumentali e di laboratorio (ecografia addominale standard / EUS, TC, RM, FNA / biopsia / dosaggio di oncomarkers ed amilasi del contenuto cistico) è stato prescelto per l’acquisizione di tutti questi dati in virtù di precisi criteri di specificità, sensibilità ed accuratezza diagnostica forniti dalla letteratura scientifica internazionale. Per ogni sottogruppo di tumore cistico del pancreas viene proposto, infine, il piano terapeutico accreditato di miglior successo, sempre secondo la comune opinione scientifica internazional

The two oxygen-regulated subunits of cytochrome c oxidase in Dictyostelium discoideum derive from a common ancestor

AbstractThe two smallest polypeptide components of D. discoideum cytochrome c oxidase, whose alternative expression depends on oxygen concentration [Schiavo G. and Bisson R. (1989) J. Biol. Chem. 264, 7129-7134], have been partially sequenced. They show 45$ homology and are isoforms of the same subunit, which must be encoded on two different genes

Site-Directed Mutagenesis of the Chlorophyll-Binding Sites Modulates Excited-State Lifetime and Chlorophyll-Xanthophyll Energy Transfer in the Monomeric Light-Harvesting Complex CP29

We combine site-directed mutagenesis with picosecond time-resolved fluorescence and femtosecond transient absorption (TA) spectroscopies to identify excitation energy transfer (EET) processes between chlorophylls (Chls) and xanthophylls (Xant) in the minor antenna complex CP29 assembled inside nanodiscs, which result in quenching. When compared to WT CP29, a longer lifetime was observed in the A(2) mutant, missing Chl a612, which closely interacts with Xant Lutein in site L1. Conversely, a shorter lifetime was obtained in the A(5) mutant, in which the interaction between Chl a603 and Chl a609 is strengthened, shifting absorption to lower energy and enhancing Chl-Xant EET. Global analysis of TA data indicated that EET from Chl a Q(y) to a Car dark state S* is active in both the A(2) and A(5) mutants and that their rate constants are modulated by mutations. Our study provides experimental evidence that multiple Chl-Xant interactions are involved in the quenching activity of CP29

Ubiquitination of Alzheimer's-related tau protein affects liquid-liquid phase separation in a site- and cofactor-dependent manner

The formation of biomolecular condensates has emerged as a crucial player both in neuronal physiology and neurodegeneration. Phase separation of the Alzheimer's related protein tau into liquid condensates is facilitated by polyanions and is regulated by post-translational modifications. Given the central role of ubiquitination in proteostasis regulation and signaling, we investigated the behavior of monoubiquitinated tau during formation of condensates. We ubiquitinated the lysine-rich, four-repeat domain of tau either unspecifically via enzymatic conjugation or in a position-specific manner by semisynthesis. Ubiquitin conjugation at specific sites weakened multivalent tau/RNA interactions and disfavored tau/heparin condensation. Yet, heterogeneous ubiquitination was tolerated during phase separation and stabilized droplets against aggregation-linked dissolution. Thus, we demonstrated that cofactor chemistry and site of modification affect the mesoscopic and molecular signatures of ubiquitinated tau condensates. Our findings suggest that ubiquitination could influence the physiological states and pathological transformations of tau in cellular condensates