Mitochondrial protein synthesis adapts to influx of nuclear-encoded protein.

Mitochondrial ribosomes translate membrane integral core subunits of the oxidative phosphorylation system encoded by mtDNA. These translation products associate with nuclear-encoded, imported proteins to form enzyme complexes that produce ATP. Here, we show that human mitochondrial ribosomes display translational plasticity to cope with the supply of imported nuclear-encoded subunits. Ribosomes expressing mitochondrial-encoded COX1 mRNA selectively engage with cytochrome c oxidase assembly factors in the inner membrane. Assembly defects of the cytochrome c oxidase arrest mitochondrial translation in a ribosome nascent chain complex with a partially membrane-inserted COX1 translation product. This complex represents a primed state of the translation product that can be retrieved for assembly. These findings establish a mammalian translational plasticity pathway in mitochondria that enables adaptation of mitochondrial protein synthesis to the influx of nuclear-encoded subunits

Oms1 associates with cytochrome c oxidase assembly intermediates to stabilize newly synthesized Cox1.

The mitochondrial cytochromecoxidase assembles in the inner membrane from subunits of dual genetic origin. The assembly process of the enzyme is initiated by membrane insertion of the mitochondria-encoded Cox1 subunit. During complex maturation, transient assembly intermediates, consisting of structural subunits and specialized chaperone-like assembly factors, are formed. In addition, cofactors such as heme and copper have to be inserted into the nascent complex. To regulate the assembly process, the availability of Cox1 is under control of a regulatory feedback cycle, in which translation of the COX1 mRNA is stalled when assembly intermediates of Cox1 accumulate through inactivation of the translational activator Mss51. Here we have isolated a cytochromecoxidase assembly intermediate in preparatory scale fromcoa1Δmutant cells using Mss51 as a bait. We demonstrate that at this stage of assembly the complex has not yet incorporated the heme a cofactors. Using quantitative mass spectrometry, we defined the protein composition of the assembly intermediate and unexpectedly identified the putative methyltransferase Oms1 as a constituent. Our analyses show that Oms1 participates in cytochromecoxidase assembly by stabilizing newly synthesized Cox1

Cooperation between COA6 and SCO2 in COX2 maturation during cytochrome c oxidase assembly links two mitochondrial cardiomyopathies.

Three mitochondria-encoded subunits form the catalytic core of cytochrome c oxidase, the terminal enzyme of the respiratory chain. COX1 and COX2 contain heme and copper redox centers, which are integrated during assembly of the enzyme. Defects in this process lead to an enzyme deficiency and manifest as mitochondrial disorders in humans. Here we demonstrate that COA6 is specifically required for COX2 biogenesis. Absence of COA6 leads to fast turnover of newly synthesized COX2 and a concomitant reduction in cytochrome c oxidase levels. COA6 interacts transiently with the copper-containing catalytic domain of newly synthesized COX2. Interestingly, similar to the copper metallochaperone SCO2, loss of COA6 causes cardiomyopathy in humans. We show that COA6 and SCO2 interact and that corresponding pathogenic mutations in each protein affect complex formation. Our analyses define COA6 as a constituent of the mitochondrial copper relay system, linking defects in COX2 metallation to cardiac cytochrome c oxidase deficiency

Regiospecific analysis of Mono and Diglycerides in Glycerolysis products by GC x GC TOF-MS.

Comprehensive bidimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOF-MS) was used for the characterization of regiospecific mono- and diglycerides (MG-DG) content in the glycerolysis products derived from five different lipids included lard (LA), sun flower seed oil (SF), corn oil (CO), butter (BU), and palm oil (PA). The combination of fast and high temperature non-orthogonal column set namely DB17ht (6 m × 0.10 mm × 0.10 μm) as the primary column and SLB-5 ms (60 cm × 0.10 mm × 0.10 μm) as the secondary column was applied in this work. System configuration involved high oven ramp temperature to obtain precise mass spectral identification and highest effluent’s resolution. 3-Monopalmitoyl-sn-glycerol (MG 3-C16) was the highest concentration in LA, BU and PA while monostearoyl-sn-glycerol (MG C18) in CO and 1,3-dilinoleol-rac-glycerol (DG C18:2c) in SF. Principal component analysis accounted 82% of variance using combination of PC1 and PC2. The presence of monostearoyl-sn-glycerol (MG C18), 3-Monopalmitoyl-sn-glycerol (MG 3-C16), 1,3-dilinoleol-rac-glycerol (DG C18:2c), 1,3-dipalmitoyl-glycerol (DG 1,3-C16), and 1,3-dielaidin (DG C18:1t) caused differentiation of the samples tested

Campodéidés endogés de l'Ouest des Etats-Unis (Washington, Orégon, Californie, Arizona, (suite)

Bareth Camille, Condé B. Campodéidés endogés de l'Ouest des Etats-Unis (Washington, Orégon, Californie, Arizona, (suite). In: Bulletin mensuel de la Société linnéenne de Lyon, 27ᵉ année, n°9, novembre 1958. pp. 265-276

Campodéidés endogés de l'Ouest des Etats-Unis (Washington, Orégon, Californie, Arizona)

Condé B., Bareth Camille. Campodéidés endogés de l'Ouest des Etats-Unis (Washington, Orégon, Californie, Arizona). In: Bulletin mensuel de la Société linnéenne de Lyon, 27ᵉ année, n°8, octobre 1958. pp. 226-248

Diploures campodéidés des grottes du Pendjab (Simlacampa clayae)

Four new specimens of Simlacampa clayae Condé, found in two caves in Pundjab (India), give opportunity to improve the original diagnosis and to describe two males and one immature

Diploures campodéidés des grottes du Pendjab (\u3cem\u3eSimlacampa clayae\u3c/em\u3e)

Four new specimens of Simlacampa clayae Condé, found in two caves in Pundjab (India), give opportunity to improve the original diagnosis and to describe two males and one immature