Cytochrome c signalosome in mitochondria

Cytochrome c delicately tilts the balance between cell life (respiration) and cell death (apoptosis). Whereas cell life is governed by transient electron transfer interactions of cytochrome c inside the mitochondria, the cytoplasmic adducts of cytochrome c that lead to cell death are amazingly stable. Interestingly, the contacts of cytochrome c with its counterparts shift from the area surrounding the heme crevice for the redox complexes to the opposite molecule side when the electron flow is not necessary. The cytochrome c signalosome shows a higher level of regulation by post-translational modifications—nitration and phosphorylation—of the hemeprotein. Understanding protein interfaces, as well as protein modifications, would puzzle the mitochondrial cytochrome c-controlled pathways out and enable the design of novel drugs to silence the action of pro-survival and pro-apoptotic partners of cytochrome c.Spanish Ministry of Science and Innovation BFU2009-07190Andalusian Government BIO198 P08-CVI-387

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

Yeast ribosomal protein L40 assembles late into precursor 60 S ribosomes and is required for their cytoplasmic maturation

Background: The contribution of ribosomal proteins to ribosome assembly and function is often not well understood. Results: L40 assembles within the cytoplasm into pre-60 S subunits and is required for Nmd3 and Rlp24 recycling. Conclusion: L40 contributes to formation of 60 S subunits competent for subunit joining and translation elongation. Significance: Our analysis of L40 function reveals an additional step during cytoplasmic pre-60 S maturation eventsMinisterio de Ciencia e Innovación BFU2010-15690Junta de Andalucía CVI-271, P08-CVI-03508Swiss National Science Foundation PP00P3_12334

Site-directed Mutagenesis of Cytochromec 6 from Synechocystissp. PCC 6803

This paper reports the first site-directed mutagenesis analysis of any cytochrome c 6, a heme protein that performs the same function as the copper-protein plastocyanin in the electron transport chain of photosynthetic organisms. Photosystem I reduction by the mutants of cytochromec 6 from the cyanobacteriumSynechocystis sp. PCC 6803 has been studied by laser flash absorption spectroscopy. Their kinetic efficiency and thermodynamic properties have been compared with those of plastocyanin mutants from the same organism. Such a comparative study reveals that aspartates at positions 70 and 72 in cytochrome c 6 are located in an acidic patch that may be isofunctional with the well known “south-east” patch of plastocyanin. Calculations of surface electrostatic potential distribution in the mutants of cytochromec 6 and plastocyanin indicate that the changes in protein reactivity depend on the surface electrostatic potential pattern rather than on the net charge modification induced by mutagenesis. Phe-64, which is close to the heme group and may be the counterpart of Tyr-83 in plastocyanin, does not appear to be involved in the electron transfer to photosystem I. In contrast, Arg-67, which is at the edge of the cytochrome c 6 acidic area, seems to be crucial for the interaction with the reaction center.Dirección General de Investigación Científica y Técnica (DGICYT, Grant PB96-1381)European Union (EU, CHRX-CT94-0540 and ERB-FMRX-CT98-0218)Junta de Andalucía (PAI, CVI-0198

The impact of a scientific argumentation electronic rubric on the blended learning methodology

Las innovaciones tecnológicas y su impacto en la educación son un importante contenido curricular en la formación inicial del grado en Pedagogía. Los rápidos cambios del desarrollo tecnológico dejan obsoletos los contenidos en esta formación, por lo que necesitamos formar en argumentación científica y tecnológica para hacer frente a innovaciones que aún no existen. Esto implica desarrollar competencias digitales y una argumentación científica y tecnológica con nuevas metodologías y tecnologías que ayuden a favorecer dichas competencias. El presente estudio pretende medir el impacto producido por una metodología y e-rúbrica de argumentación -extraída del modelo de Toulmin- junto con la autoevaluación sobre los procesos de argumentación y las calificaciones de 30 estudiantes del grado de Pedagogía en modalidad b-learning. Para tal fin, se plantea una investigación mixta: por un lado, un análisis cualitativo de 262 anotaciones dadas por los estudiantes a dos ejercicios de argumentación (uno con y otro sin la e-rúbrica) sobre dos casos de innovación tecnológica similares; y por otro, un análisis cuantitativo y correlacional de la autoevaluación por los estudiantes y las evaluaciones del docente mediante el estadístico Wilcoxonde. Los resultados permitieron comprobar el impacto positivo de la e-rúbrica de argumentación, y su correlación (Z=-2,440; Z=-3,276 y Z=-2,783) con las mejores calificaciones, favoreciendo argumentaciones más elaboradas

Gestión del agua doméstica urbana en hermosillo (sonora, méxico)

Este estudio presenta un análisis del crecimiento urbano en la zona urbana de Hermosillo (Sonora, México) con respecto a la variable consumo de agua doméstica. Se describe la zona de estudio que se localiza en una franja del desierto de Sonora y se analiza el crecimiento demográfico de la ciudad en un periodo de seis décadas relacionado con el aumento de la superficie urbana. Así también, se efectúa el análisis de la densidad de población y su relación con las políticas de gestión urbana del agua. Finalmente, se evidencia el funcionamiento del modelo de gestión del agua doméstica en la ciudad, y se establece la ruta para incursionar en un nuevo modelo de gestión más sustentable

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

A Fatal Case of Generalized Lysosomal Storage Disease in an Infant.

Gangliosidoses are a heterogeneous group of lysosomal storage diseases with an autosomal recessive trait, which are characterized by the intracellular accumulation of gangliosides in several tissues, mainly in neurons. This condition causes a progressive neurodegenerative disorder with varied clinical presentations. Depending on the severity of the enzymatic defect, gangliosidoses show different rates of clinical progression and organ involvement; poor residual enzyme activity is seen in more aggressive forms (infantile and juvenile subtypes) leading to early death whereas cases with better residual enzyme activity have a late onset in adult life and a milder clinical course. Autopsy findings of a 7 month-old girl with histological and ultrastructural changes consistent with gangliosidosis are presented

Voltammetric study of the adsorbed thermophilic plastocyanin from Phormidium laminosum up to 90 °c

Redox thermodynamics and kinetics of plastocyanin from Phormidium laminosum, and of azurin from Pseudonomas aeruginosa, have been investigated as a function of temperature by protein film voltammetry. To this purpose, both proteins have been physisorbed on a pyrolytic graphite edge electrode. A pronounced negative shift of the plastocyanin standard potential, compared to a slight shift in the case of azurin, has been found upon increasing the temperature. Hence, significant conformational and/or solvation changes accompany the redox conversion of plastocyanin. Lower electron transfer rate constants (by c.a. one order of magnitude) and higher activation enthalpies have been found for plastocyanin as compared to azurin. The voltammetric response of azurin vanishes irreversibly at temperatures close to 60 °C, whereas the redox properties of plastocyanin remain unaltered, except for some loss of electroactive protein, after heating the electrode at temperatures as high as 90 °C.Ministerio de Economía y Competitividad CTQ 2008-00371, BFU2009-07190Junta de Andalucía P07-FQM-02492, P06-CVI-0171

Site-directed Mutagenesis of Cytochromec 6 from Anabaena Species PCC 7119

A number of surface residues of cytochromec 6 from the cyanobacterium Anabaenasp. PCC 7119 have been modified by site-directed mutagenesis. Changes were made in six amino acids, two near the heme group (Val-25 and Lys-29) and four in the positively charged patch (Lys-62, Arg-64, Lys-66, and Asp-72). The reactivity of mutants toward the membrane-anchored complex photosystem I was analyzed by laser flash absorption spectroscopy. The experimental results indicate that cytochrome c 6 possesses two areas involved in the redox interaction with photosystem I: 1) a positively charged patch that may drive its electrostatic attractive movement toward photosystem I to form a transient complex and 2) a hydrophobic region at the edge of the heme pocket that may provide the contact surface for the transfer of electrons to P700. The isofunctionality of these two areas with those found in plastocyanin (which acts as an alternative electron carrier playing the same role as cytochromec 6) are evident