8 results on '"Alfieri, Andrea"'
Search Results
2. The structural bases for agonist diversity in an Arabidopsis thaliana glutamate receptor-like channel.
- Author
-
Alfieri, Andrea, Doccula, Fabrizio G., Pederzoli, Riccardo, Grenzi, Matteo, Bonza, Maria Cristina, Luoni, Laura, Candeo, Alessia, Armada, Neli Romano, Barbiroli, Alberto, Valentini, Gianluca, Schneider, Thomas R., Bassi, Andrea, Bolognesi, Martino, Nardini, Marco, and Costa, Alex
- Subjects
ARABIDOPSIS thaliana ,GLUTAMIC acid ,AMINO acids ,POLLEN tube ,ION channels - Abstract
Arabidopsis thaliana glutamate receptor-like (GLR) channels are amino acid-gated ion channels involved in physiological processes including wound signaling, stomatal regulation, and pollen tube growth. Here, fluorescence microscopy and genetics were used to confirm the central role of GLR3.3 in the amino acid-elicited cytosolic Ca
2+ increase in Arabidopsis seedling roots. To elucidate the binding properties of the receptor, we biochemically reconstituted the GLR3.3 ligand-binding domain (LBD) and analyzed its selectivity profile; our binding experiments revealed the LBD preference for l-Glu but also for sulfur-containing amino acids. Furthermore, we solved the crystal structures of the GLR3.3 LBD in complex with 4 different amino acid ligands, providing a rationale for how the LBD binding site evolved to accommodate diverse amino acids, thus laying the grounds for rational mutagenesis. Last, we inspected the structures of LBDs from nonplant species and generated homology models for other GLR isoforms. Our results establish that GLR3.3 is a receptor endowed with a unique amino acid ligand profile and provide a structural framework for engineering this and other GLR isoforms to investigate their physiology. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
3. Unilateral Trade Preferences in the EU: An Empirical Assessment for the Case of Mozambican Exports.
- Author
-
Cirera, Xavier and Alfieri, Andrea
- Abstract
Unilateral trade preferences are one of the most important instruments offered by developed countries to foster developing country exports. This paper analyzes the impact of unilateral trade preferences on developing countries by focusing on the experience of Mozambique. In this paper, we analyze whether unilateral preferences offered by the EU are "valuable" for Mozambican exporters based on the impact on preferential margins, utilization rates, and export prices. We use a detailed dataset with cif unit values at HS8-digits level covering the period 2000-2007. Our findings indicate that (i) for a large number of product lines, export margins are zero; (ii) utilization rates are generally high; however, (iii) this does not translate into a positive price margins captured by Mozambican exporters compared to MFN competitors. These findings cast doubts on the "value" of preferences and their potential impact on developing country exports. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
4. Inscuteable and NuMA proteins bind competitively to Leu-Gly-Asn repeat-enriched protein (LGN) during asymmetric cell divisions.
- Author
-
Culurgioni, Simone, Alfieri, Andrea, Pendolino, Valentina, Laddomada, Federica, and Mapelli, Marina
- Subjects
CELL division ,CRYSTAL structure ,DROSOPHILA ,NUCLEAR proteins ,BASAL metabolism - Abstract
Coupling of spindle orientation to cellular polarity is a prerequisite for epithelial asymmetric cell divisions. The current view posits that the adaptor Inscuteable (Insc) bridges between Par3 and the spindle tethering machinery assembled on NuMA:LGN:Gai
GDP , thus triggering apico-basal spindle orientation. The crystal structure of the Drosophila ortholog of LGN (known as Pins) in complex with Insc reveals a modular interface contributed by evolutionary conserved residues. The structure also identifies a positively charged patch of LGN binding to an invariant EPE-motif present on both Insc and NuMA. In vitro competition assays indicate that Insc competes with NuMA for LGN binding, displaying a higher affinity, and that it is capable of opening the LGN conformational switch. The finding that Insc and NuMA are mutually exclusive interactors of LGN challenges the established model of force generators assembly, which we revise on the basis of the newly discovered biochemical properties of the intervening components. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
5. Revealing the moonlighting role of NADP in the structure of a flavin-containing mónooxygenase.
- Author
-
Alfieri, Andrea, Malito, Enrico, Orru, Roberto, Fraaije, Marco W., and Mattevi, Andrea
- Subjects
MONOOXYGENASES ,FLAVINS ,XENOBIOTICS ,METABOLISM ,ELECTRON distribution ,CATALYSIS - Abstract
Flavin-containing monooxygenases (FMOs) are, after cytochromes P450, the most important monooxygenase system in humans and are involved in xenobiotics metabolism and variability in drug response. The x-ray structure of a soluble prokaryotic FMO from Methylophaga sp. strain SK1 has been solved at 2.6-Å resolution and is now the protein of known structure with the highest sequence similarity to human FMOs. The structure possesses a two-domain architecture, with both FAD and NADP
+ well defined by the electron density maps. Biochemical analysis shows that the prokaryotic enzyme shares many functional properties with mammalian FMOs, including substrate specificity and the ability to stabilize the hydroperoxyflavin intermediate that is crucial in substrate oxygenation. On the basis of their location in the structure, the nicotinamide ring and the adjacent ribose of NADP+ turn out to be an integral part of the catalytic site being actively engaged in the stabilization of the oxygenating intermediate. This feature suggests that NADP(H) has a moonlighting role, in that it adopts two binding modes that allow it to function in both flavin reduction and oxygen reactivity modulation, respectively. We hypothesize that a relative domain rotation is needed to bring NADP(H) to these distinct positions inside the active site. Localization of mutations in human FMO3 that are known to cause trimethylaminuria (fish-odor syndrome) in the elucidated FMO structure provides a structural explanation for their biological effects. [ABSTRACT FROM AUTHOR]- Published
- 2008
- Full Text
- View/download PDF
6. Structure of the monooxygenase component of a two-component flavoprotein monooxygenase.
- Author
-
Alfieri, Andrea, Fersini, Francesco, Ruangchan, Nantidaporn, Prongjit, Methinee, Chaiyent, Pimchai, and Mattevi, Andrea
- Subjects
MONOOXYGENASES ,OXYGENASES ,FLAVOPROTEINS ,PROTEINS ,FLAVINS - Abstract
p-Hydroxyphenylacetate hydroxylase from Acinetobacter baumannii is a two-component system consisting of a NADH-dependent FMN reductase and a monooxygenase ((2) that uses reduced FMN as substrate. The crystal structures of C
2 in the ligand-free and substrate-bound forms reveal a preorganized pocket that binds reduced FMN without large conformational changes. The Phe-266 side chain swings out to provide the space for binding p-hydroxyphenylacetate that is oriented orthogonal to the flavin ring. The geometry of the substrate-binding site of C2 is significantly different from that of p-hydroxybenzoate hydroxylase, a single-component flavoenzyme that catalyzes a similar reaction. The C2 overall structure resembles the folding of medium-chain acyl-CoA dehydrogenase. An outstanding feature in the C2 structure is a cavity located in front of reduced FMN; it has a spherical shape with a 1.9-Šradius and a 29-ų volume and is interposed between the flavin C4a atom and the substrate atom to be hydroxylated. The shape and position of this cavity are perfectly fit for housing the oxygen atoms of the flavin C4a-hydroperoxide intermediate that is formed upon reaction of the C2 -bound reduced flavin with molecular oxygen. The side chain of His-396 is predicted to act as a hydrogen-bond donor to the oxygen atoms of the intermediate. This architecture promotes the nucleophilic attack of the substrate onto the terminal oxygen of the hydroperoxyflavin. Comparative analysis with the structures of other flavoenzymes indicates that a distinctive feature of monooxygenases is the presence of specific cavities that encapsulate and stabilize the crucial hydroperoxyflavin intermediate. [ABSTRACT FROM AUTHOR]- Published
- 2007
- Full Text
- View/download PDF
7. Crystal structure of a Baeyer-Villiger monooxygenase.
- Author
-
Malito, Enrico, Alfieri, Andrea, Fraaije, Marco W., and Mattevi, Andrea
- Subjects
MONOOXYGENASES ,FLAVINS ,COENZYMES ,CATALYSTS ,STRUCTURE-activity relationships ,BINDING sites ,BIOCHEMISTRY - Abstract
Flavin-containing Baeyer-Villiger monooxygenases employ NADPH and molecular oxygen to catalyze the insertion of an oxygen atom into a carbon-carbon bond of a carbonylic substrate. These enzymes can potentially be exploited in a variety of biocatalytic applications given the wide use of Baeyer-Villiger reactions in synthetic organic chemistry. The catalytic activity of these enzymes involves the formation of two crucial intermediates: a flavin peroxide generated by the reaction of the reduced flavin with molecular oxygen and the "Criegee" intermediate resulting from the attack of the flavin peroxide onto the substrate that is being oxygenated. The crystal structure of phenylacetone monooxygenase, a Baeyer-Villiger monooxygenase from the thermophilic bacterium Thermobifida fusca, exhibits a two-domain architecture resembling that of the disulfide oxidoreductases. The active site is located in a cleft at the domain interface. An arginine residue lays above the flavin ring in a position suited to stabilize the negatively charged flavin-peroxide and Criegee intermediates. This amino acid residue is predicted to exist in two positions; the "IN" position found in the crystal structure and an "OUT" position that allows NADPH to approach the flavin to reduce the cofactor. Domain rotations are proposed to bring about the conformational changes involved in catalysis. The structural studies highlight the functional complexity of this class of flavoenzymes, which coordinate the binding of three substrates (molecular oxygen, NADPH, and phenylacetone) in proximity of the flavin cofactor with formation of two distinct catalytic intermediates. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
8. Hexameric NuMA:LGN structures promote multivalent interactions required for planar epithelial divisions.
- Author
-
Pirovano, Laura, Culurgioni, Simone, Carminati, Manuel, Alfieri, Andrea, Monzani, Silvia, Cecatiello, Valentina, Gaddoni, Chiara, Rizzelli, Francesca, Foadi, James, Pasqualato, Sebastiano, and Mapelli, Marina
- Abstract
Cortical force generators connect epithelial polarity sites with astral microtubules, allowing dynein movement to orient the mitotic spindle as astral microtubules depolymerize. Complexes of the LGN and NuMA proteins, fundamental components of force generators, are recruited to the cortex by Gαi-subunits of heterotrimeric G-proteins. They associate with dynein/dynactin and activate the motor activity pulling on astral microtubules. The architecture of cortical force generators is unknown. Here we report the crystal structure of NuMA:LGN hetero-hexamers, and unveil their role in promoting the assembly of active cortical dynein/dynactin motors that are required in orchestrating oriented divisions in polarized cells. Our work elucidates the basis for the structural organization of essential spindle orientation motors. LGN and NuMA link epithelial polarity sites with astral microtubules and associate with dynein, but the architecture of such cortical force-generating complexes is unknown. Here, the authors report the crystal structure of NuMA:LGN hetero-hexamers, and unveil their role in promoting the assembly of active cortical dynein/dynactin motors. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.