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1.
EMBO Rep ; 21(12): e51015, 2020 12 03.
Artículo en Inglés | MEDLINE | ID: mdl-33016568

RESUMEN

Respiratory chains are crucial for cellular energy conversion and consist of multi-subunit complexes that can assemble into supercomplexes. These structures have been intensively characterized in various organisms, but their physiological roles remain unclear. Here, we elucidate their function by leveraging a high-resolution structural model of yeast respiratory supercomplexes that allowed us to inhibit supercomplex formation by mutation of key residues in the interaction interface. Analyses of a mutant defective in supercomplex formation, which still contains fully functional individual complexes, show that the lack of supercomplex assembly delays the diffusion of cytochrome c between the separated complexes, thus reducing electron transfer efficiency. Consequently, competitive cellular fitness is severely reduced in the absence of supercomplex formation and can be restored by overexpression of cytochrome c. In sum, our results establish how respiratory supercomplexes increase the efficiency of cellular energy conversion, thereby providing an evolutionary advantage for aerobic organisms.


Asunto(s)
Citocromos c , Proteínas de Saccharomyces cerevisiae , Citocromos c/genética , Transporte de Electrón , Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
2.
Food Microbiol ; 30(1): 239-44, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-22265307

RESUMEN

In the present work, single and mixed cereal substrates were fermented with lactic acid bacteria to study and compare the effect of the media formulation on fermentation parameters. Three cereal flours namely malt, barley and barley mixed with malt (barley-malt) were selected and fermented with two probiotic strains: Lactobacillus plantarum (NCIMB 8826) and Lactobacillus acidophilus (NCIMB 8821). The effect of the single and mixed cereal flour suspensions on the fermentation of these two strains of lactic acid bacteria (LAB) was studied at an incubation temperature of 30 °C for 28 h. It was found that the LAB growth was enhanced in media containing malt and significant amounts of lactic acid were produced (0.5-3.5 g/L). A cell concentration between 7.9 and 8.5 Log10 CFU/mL and a pH below 4.0 was achieved within 6 h of fermentation. Though the cell populations in the mixed culture fermentations of mixed substrates were similar to the ones obtained with single cereal flours, significant differences in the production of lactic acid were observed. These results suggest that the functional and organoleptic properties of these cereal-based probiotic drinks could be considerably modified through changes in the substrate or inocula composition.


Asunto(s)
Bebidas/microbiología , Grano Comestible/microbiología , Fermentación , Lactobacillus acidophilus/crecimiento & desarrollo , Lactobacillus plantarum/crecimiento & desarrollo , Probióticos , Recuento de Colonia Microbiana , Grano Comestible/química , Manipulación de Alimentos/métodos , Microbiología de Alimentos , Concentración de Iones de Hidrógeno
3.
Nat Struct Mol Biol ; 26(1): 50-57, 2019 01.
Artículo en Inglés | MEDLINE | ID: mdl-30598556

RESUMEN

Respiratory chain complexes execute energy conversion by connecting electron transport with proton translocation over the inner mitochondrial membrane to fuel ATP synthesis. Notably, these complexes form multi-enzyme assemblies known as respiratory supercomplexes. Here we used single-particle cryo-EM to determine the structures of the yeast mitochondrial respiratory supercomplexes III2IV and III2IV2, at 3.2-Å and 3.5-Å resolutions, respectively. We revealed the overall architecture of the supercomplex, which deviates from the previously determined assemblies in mammals; obtained a near-atomic structure of the yeast complex IV; and identified the protein-protein and protein-lipid interactions implicated in supercomplex formation. Take together, our results demonstrate convergent evolution of supercomplexes in mitochondria that, while building similar assemblies, results in substantially different arrangements and structural solutions to support energy conversion.


Asunto(s)
Microscopía por Crioelectrón/métodos , Animales , Transporte de Electrón/fisiología , Humanos , Metabolismo de los Lípidos , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Unión Proteica , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/ultraestructura
4.
Nat Struct Mol Biol ; 24(10): 866-869, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-28892042

RESUMEN

Mammalian mitochondrial ribosomes (mitoribosomes) have less rRNA content and 36 additional proteins compared with the evolutionarily related bacterial ribosome. These differences make the assembly of mitoribosomes more complex than the assembly of bacterial ribosomes, but the molecular details of mitoribosomal biogenesis remain elusive. Here, we report the structures of two late-stage assembly intermediates of the human mitoribosomal large subunit (mt-LSU) isolated from a native pool within a human cell line and solved by cryo-EM to ∼3-Šresolution. Comparison of the structures reveals insights into the timing of rRNA folding and protein incorporation during the final steps of ribosomal maturation and the evolutionary adaptations that are required to preserve biogenesis after the structural diversification of mitoribosomes. Furthermore, the structures redefine the ribosome silencing factor (RsfS) family as multifunctional biogenesis factors and identify two new assembly factors (L0R8F8 and mt-ACP) not previously implicated in mitoribosomal biogenesis.


Asunto(s)
Ribosomas Mitocondriales/ultraestructura , Subunidades Ribosómicas Grandes de Eucariotas/ultraestructura , Microscopía por Crioelectrón , Humanos , Factores de Tiempo
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