Cytochrome c: Surfing Off of the Mitochondrial Membrane on the Tops of Complexes III and IV

The proper arrangement of protein components within the respiratory electron transport chain is nowadays a matter of intense debate, since altering it leads to cell aging and other related pathologies. Here, we discuss three current views-the so-called solid, fluid and plasticity models-which describe the organization of the main membrane-embedded mitochondrial protein complexes and the key elements that regulate and/or facilitate supercomplex assembly. The soluble electron carrier cytochrome c has recently emerged as an essential factor in the assembly and function of respiratory supercomplexes. In fact, a 'restricted diffusion pathway' mechanism for electron transfer between complexes III and IV has been proposed based on the secondary, distal binding sites for cytochrome c at its two membrane partners recently discovered. This channeling pathway facilitates the surfing of cytochrome c on both respiratory complexes, thereby tuning the efficiency of oxidative phosphorylation and diminishing the production of reactive oxygen species. The well-documented post-translational modifications of cytochrome c could further contribute to the rapid adjustment of electron flow in response to changing cellular conditions.Spanish Ministry of Economy and Competitiveness (BFU2015-71017/BMC MINECO/FEDER and PGC2018-096049-B-I00 BIO/BMC MICINN/FEDER, EU

Long distance electron transfer through the aqueous solution between redox partner proteins

Despite the importance of electron transfer between redox proteins in photosynthesis and respiration, the inter-protein electron transfer rate between redox partner proteins has never been measured as a function of their separation in aqueous solution. Here, we use electrochemical tunneling spectroscopy to show that the current between two protein partners decays along more than 10 nm in the solution. Molecular dynamics simulations reveal a reduced ionic density and extended electric field in the volume confined between the proteins. The distance-decay factor and the calculated local barrier for electron transfer are regulated by the electrochemical potential applied to the proteins. Redox partners could use electrochemically gated, long distance electron transfer through the solution in order to conciliate high specificity with weak binding, thus keeping high turnover rates in the crowded environment of cells.España, MINECO BFU2015-71017-P/España, Gobierno de Andalucía (BIO198)Comisión de Universidades e Investigación del Departamento de Innovación, Universidades y Empresa de la Generalitat de Catalunya.(2017 SGR 1442, 2014 SGR 1442, and 2017 SGR 1189

La negociación, piedra angular de las investigaciones

The first section of this paper focuses onthe importance of negotiation processesrelated to research and evaluation. Thisimportance is based on five issues: ethicsin production processes, knowledge scope,rigorous inquiry, efficiency of development-oriented findings, and strategy tomaintain contexts in which research andparticipant learning can take place. Thedifferent phases of the negotiation processare also presented: initial, processing andreporting, the last one of special importance.The requirements, types, characteristicsand operation processes of the reportingphase are discussed. The secondsection of this paper provides in the formof an example a specific case of negotiationfrom a qualitative investigation aboutimmigrant families’ participation at school.Its different phases, demands and virtualitiesare discussed. The paper finished withsome final considerations and references.El artículo consta de dos partes complementarias. Una de ellas trata de explicar la importancia de los procesos de negociación en la realización de investigaciones y evaluaciones. Importancia que se basa en cinco razones: ética de los procesos de producción y aplicación del conocimiento,rigor de las indagaciones, eficacia de los hallazgos para la mejora, estrategia para mantener contextos en que se pueda investigar y aprendizaje de los y las participantes. Se plantean las distintas fases de la negociación: inicial, de proceso y de informes, con especial atención a estaúltima. De ella se estudian las exigencias,los tipos, las características y los procedimientos de actuación.La segunda parte muestra, a modo de ejemplo, un caso concreto de negociación de una investigación cualitativa sobre la participación de familias inmigrantes en la escuela, con sus diversas fases, exigencias y virtualidades.Se cierra el artículo con algunas consideraciones finales y con la correspondiente bibliografía

La participación de las familias de alumnos y alumnas inmigrantes en las instituciones educativas

Los fenómenos de la inmigración y de la interculturalidad han cobrado en España un extraordinario protagonismo no sólo por sus dimensiones sino por la variedad de la procedencia de inmigrantes y la complejidad de las situaciones migratorias. El trabajo del grupo consistía en explorar cuál es la respuesta de la escuela a esta situación sobrevenida de forma casi súbita y cuál es la dinámica de participación de las familias en ella.En este artículo se expone el proceso de una investigación etnográfica realizada en seis centros escolares de Málaga (España) durante los años 2007/2009 sobre la participación de las familias de alumnos y alumnas inmigrantes en la escuela. La investigación se negocia con los centros elegidos (4 de Primaria y 2 de Secundaria) en los que se realizan entrevistas, observaciones, grupos de discusión y se analizan documentos relacionados con la temática del trabajo. Se desarrollan los principales resultados, tanto relativos al proceso como al foco de estudio, destacando las buenas prácticas que se están llevando a cabo en los centros y que pueden servir de referencia en otros contextos escolares.Los informes de la investigación han sido devueltos a los centros para su negociación con los participantes. Aquí se plantean las conclusiones de carácter general que se han extraído de los seis centros en los que se realizó la exploración. Hay por consiguiente, cuestiones que se refieren a todos y otras que son peculiares de uno o algunos de ellos

Structural and functional characterization of phosphomimetic mutants of cytochrome c at threonine 28 and serine 47

Protein function is frequently modulated by post-translational modifications of specific residues. Cytochrome c, in particular, is phosphorylated in vivo at threonine 28 and serine 47. However, the effect of such modifications on the physiological functions of cytochrome c – namely, the transfer of electrons in the respiratory electron transport chain and the triggering of programmed cell death – is still unknown. Here we replace each of these two residues by aspartate, in order to mimic phosphorylation, and report the structural and functional changes in the resulting cytochrome c variants. We find that the T28D mutant causes a 30-mV decrease on the midpoint redox potential and lowers the affinity for the distal site of Arabidopsis thaliana cytochrome c1 in complex III. Both the T28D and S47D variants display a higher efficiency as electron donors for the cytochrome c oxidase activity of complex IV. In both protein mutants, the peroxidase activity is significantly higher, which is related to the ability of cytochrome c to leave the mitochondria and reach the cytoplasm. We also find that both mutations at serine 47 (S47D and S47A) impair the ability of cytoplasmic cytochrome c to activate the caspases cascade, which is essential for triggering programmed cell death.Peer reviewe

Oxidative stress is tightly regulated by cytochrome c phosphorylation and respirasome factors in mitochondria

Respiratory cytochrome c has been found to be phosphorylated at tyrosine 97 in the postischemic brain upon neuroprotective insulin treatment, but how such posttranslational modification affects mitochondrial metabolism is unclear. Here, we report the structural features and functional behavior of a phosphomimetic cytochrome c mutant, which was generated by site-specific incorporation at position 97 of p-carboxymethyl-l-phenylalanine using the evolved tRNA synthetase method. We found that the point mutation does not alter the overall folding and heme environment of cytochrome c, but significantly affects the entire oxidative phosphorylation process. In fact, the electron donation rate of the mutant heme protein to cytochrome c oxidase, or complex IV, within respiratory supercomplexes was higher than that of the wild-type species, in agreement with the observed decrease in reactive oxygen species production. Direct contact of cytochrome c with the respiratory supercomplex factor HIGD1A (hypoxia-inducible domain family member 1A) is reported here, with the mutant heme protein exhibiting a lower affinity than the wild-type species. Interestingly, phosphomimetic cytochrome c also exhibited a lower caspase-3 activation activity. Altogether, these findings yield a better understanding of the molecular basis for mitochondrial metabolism in acute diseases, such as brain ischemia, and thus could allow the use of phosphomimetic cytochrome c as a neuroprotector with therapeutic applications.España, Junta de Andalucía BIO-198España MINECO BFU2015-71017/BM

The role of PKD1 in aging-related neurodegeneration: Structural and functional imaging studies

Trabajo presentado en el Second Spanish Molecular Imaging Network (SMIN) Meeting, celebrado en Madrid (España) el 26 de febrero de 2018

Respiratory complexes III and IV can each bind two molecules of cytochrome c at low ionic strength

The transient interactions of respiratory cytochrome c with complexes III and IV is herein investigated by using heterologous proteins, namely human cytochrome c, the soluble domain of plant cytochrome c1 and bovine cytochrome c oxidase. The binding molecular mechanisms of the resulting cross-complexes have been analyzed by Nuclear Magnetic Resonance and Isothermal Titration Calorimetry. Our data reveal that the two cytochrome c-involving adducts possess a 2:1 stoichiometry – that is, two cytochrome c molecules per adduct – at low ionic strength. We conclude that such extra binding sites at the surfaces of complexes III and IV can facilitate the turnover and sliding of cytochrome c molecules and, therefore, the electron transfer within respiratory supercomplexes.España, MINECO Grant Nos. BFU2010-19451/BMC and BFU2012-31670/BMCJunta de Andalucía Grant PAI, BIO198España Ministerio de Educación, y European Social Fund-ERDF AP2009-409

Tumor Phyllodes de la mama

 Introduction Phyllodes tumor (PT) is a rare tumor of the breast, representing less than 1% of all breast neoplasms (1) and 2 to 3% of fibroepithelial tumors (7). This neoplasm is classified as: Benign PT, Borderline PT and Malignant PT (Norris and Taylor-WHO) (9). Objective To carry out a review about the diagnosis and treatment of phyllodes tumor. Development PTs are fibroepithelial neoplasms that according to stromal cellularity, nuclear atypia, mitotic rate, heterologous elements are classified as: benign, borderline and malignant (1). The maximum incidence occurs between 35-55 years. Imaging diagnosis is based on the use of mammography, ultrasound, magnetic resonance imaging and radioguided core biopsy. Optimal surgical management is the fundamental tool in PT. There is controversy about the use of adjuvant treatment with radiotherapy and chemotherapy. Conclusions: PT is a benign neoplasm of the breast, surgery is the treatment of choice. The free edge greater than 1 cm recommended by the NCCN is predictive of a lower percentage of local recurrence. Complementary treatments with radiotherapy and chemotherapy are controversial. Introducción: El tumor phyllodes (TP) es un tumor raro de la mama, representa menos del 1% de todas las neoplasias de la mama (1) y el 2 a 3 % de los tumores fibroepiteliales (7). Esta neoplasia se clasifica en: TP Benigno, TP Borderline y TP Maligno (Norris y Taylor-OMS) (9). Objetivo: Realizar una revisión acerca del diagnóstico y tratamiento del tumor phyllodes. Desarrollo: Los TP son neoplasias fibroepiteliales qué de acuerdo a la celularidad estromal, atipia nuclear, tasa mitótica, elementos heterólogos son clasificados como: benignos, borderline y malignos (1). La máxima incidencia se da entre los 35-55 años. El diagnóstico por imágenes se basa en el uso de mamografía, ecografía, resonancia magnética y biopsia core radioguiada. El óptimo manejo quirúrgico constituye la herramienta fundamental en TP. Existe controversia acerca del uso de tratamiento adyuvante con radioterapia y quimioterapia.  Conclusiones: TP es una neoplasia benigna de la mama, la cirugía es el tratamiento de elección. El borde libre mayor de 1 cm recomendado por la NCCN es predictivo para un menor porcentaje de recurrencia local. Los tratamientos complementarios con radioterapia y quimioterapia son controversiales

Pragmatic eclecticism in the drawing and architecture of Luis Gutierrez Soto

[EN] Despite the extent of his work, the figure of Gutiérrez Soto is very hard to classify in the architectural context of his time. Most of his contemporaries agreed in pointing out his enormous work capacity and his excellent drawing skills. However, the diverse character of his work and his strong and uncertain personality have sometimes contributed to obscuring his figure, given the impossibility of associating it with a specific movement. His graphic legacy brings a broad narrative discourse to his built work, while sharing a pragmatic vision of architectural design. Architectural and graphic production are combined in a single language. The graphic legacy of Gutiérrez Soto runs in parallel with his life stages, reflecting an era marked by extreme circumstances. Despite this, nothing in his work seems to deviate from the norm, constituting an extraordinary legacy.[ES] Pese a lo extenso de su obra, la figura de Gutiérrez Soto resulta muy difícil de clasificar en el contexto arquitectónico de su época. La mayoría de sus coetáneos coincidieron en señalar su enorme capacidad de trabajo y sus excelentes aptitudes para el dibujo. Sin embargo, el carácter diverso de su obra y su personalidad segura e incierta, han contribuido en ocasiones a oscurecer su figura ante la imposibilidad de asociarlo con un movimiento concreto. Su legado gráfico aporta un amplio discurso narrativo a su obra construida, a la vez que comparte una visión pragmática de la arquitectura proyectada. Producción arquitectónica y producción gráfica se traban en un solo lenguaje. La herencia gráfica de Gutiérrez Soto, discurre en paralelo a sus etapas vitales, reflejo de una época marcada por circunstancias extremas. A pesar de ello, nada en su obra parece salirse de la norma y, sin embargo, en conjunto constituye una herencia extraordinaria.Raposo Grau, JF.; Salgado De La Rosa, MA.; Butragueño Diaz-Guerra, B.; Paredes Maldonado, M. (2023). Eclecticismo pragmático en el dibujo y la arquitectura de Luis Gutiérrez Soto. EGA Expresión Gráfica Arquitectónica. 28(49):286-309. https://doi.org/10.4995/ega.2023.20755286309284