1,721,105 research outputs found
Mutational analysis of the cysteine-rich region of the iron-responsive GATA factor Fep1. Role of individual cysteines as [2Fe–2S] cluster ligands
No full textFep1, the iron-dependent GATA-type transcriptional repressor of the methylotrophic yeast Pichia pastoris, has a dimeric structure and binds an iron–sulfur cluster of the [2Fe–2S] type. In this work, we extend the characterization of this protein by analysis of the optical and CD spectroscopic properties of a set of mutants where cysteines within the conserved Cys-X5-Cys-X8-Cys-X2-Cys motif have been targeted, in order to evaluate their role as [2Fe–2S] ligands. The results suggest that all four cysteine residues are essential because replacing them with serines in different combinations invariably produces a protein unable to correctly bind the [2Fe–2S] cluster
Lactoferrin, the moonlighting protein of innate immunity
Full text linkLactoferrin (Lf), a naturally occurring glycoprotein involved in innate immunity, was first discovered in bovine milk [...]
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The different affinity of the two metal-binding sites of human ferroportin drives outward directionality of transport
No full text: Ferroportin, the only known cellular iron exporter, belongs to the major facilitator superfamily of transporters, which cycle between inward-open, occluded and outward-open conformations to translocate substrates across membranes. Recently reported cryoEM structures of ferroportin identified two metal-binding sites in the central cavity of the protein, with site S1 that includes residues D39 and H43, while site S2 is formed by C326 and H507. Here we have employed fluorescence spectroscopy to evaluate the binding affinity for cobalt of human ferroportin. The results suggest that S2 has a higher affinity for cobalt than S1. Results are discussed in view of available structural data on the outward-open conformation of Fpn and of a novel structural model of the inward-open conformation, obtained with a custom implementation of AlphaFold 2. We propose a mechanism by which the outward flux of iron could be driven by the different affinity of the two sites
A bacterial homologue of the human iron exporter ferroportin
No full textA bacterial homologue of the human iron exporter ferroportin found in the predatory Gram-negative bacterium Bdellovibrio bacteriovorus has been investigated. Molecular modelling, expression in recombinant form and iron binding and transport assays demonstrate that B. bacteriovorus ferroportin (bdFpn) is indeed an orthologue of human ferroportin. Key residues corresponding to those essential for iron binding and transport in human ferroportin are conserved in the bacterial homologue and are predicted to be correctly clustered in the central cavity of the protein. Mutation of these residues grossly affects the iron binding and transport ability of bdFpn
The human iron exporter ferroportin. Insight into the transport mechanism by molecular modeling
No full textFerroportin (Fpn), a membrane protein belonging to the Major Facilitator Superfamily (MFS) of transporters, is the only vertebrate iron exporter known so far. Several Fpn mutations lead to the so-called ‘ferroportin disease’ or type 4 haemochromatosis, characterized by two distinct iron accumulation phenotypes depending on whether the mutation affects the activity of the protein or its degradation pathway. Through extensive molecular modelling analysis using the structures of all known MFS members as templates, we obtained multiple structural models of Fpn in the three mechanistically relevant conformations (inward-open, occluded and outward-open). The best models, selected on the ground of experimental data previously obtained on wild type and mutant Fpn, provide for the first time a prediction at the atomic level of the dynamics of the transporter. Based on these results, a possible mechanism for iron export is proposed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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