The protein import machinery of the mitochondrial outer membrane is comprised of a dynamic complex of proteins that
mediates translocation of cytosolic precursor proteins into or across the membrane. Several proteins within this complex
have been identified, such as Mas20p in yeast and MOM19 in Neurospora crassa. Goping et al. (1995) cloned and characterized the human homolog of Mas20p/MOM19. The 145-amino acid human
polypeptide shares high similarity with Mas20p and MOM19 within the N-terminal region, but exhibits only weak homology
to the tetratricopeptide-repeat B domain that is found in the other 2 proteins. The authors showed that human Mas20p is
targeted and inserted into the outer membrane of isolated rat heart mitochondria in the N(in)-to-C(cyto) orientation.
General function
Intracellular protein transport
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Cellular localization
Mitochondrial
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Ovarian function
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Single-Cell Transcriptomic Atlas of Primate Ovarian Aging. Wang S et al. (2020) Molecular mechanisms of ovarian aging and female age-related fertility decline remain unclear. We surveyed the single-cell transcriptomic landscape of ovaries from young and aged non-human primates (NHPs) and identified seven ovarian cell types with distinct gene-expression signatures, including oocyte and six types of ovarian somatic cells. In-depth dissection of gene-expression dynamics of oocytes revealed four subtypes at sequential and stepwise developmental stages. Further analysis of cell-type-specific aging-associated transcriptional changes uncovered the disturbance of antioxidant signaling specific to early-stage oocytes and granulosa cells, indicative of oxidative damage as a crucial factor in ovarian functional decline with age. Additionally, inactivated antioxidative pathways, increased reactive oxygen species, and apoptosis were observed in granulosa cells from aged women. This study provides a comprehensive understanding of the cell-type-specific mechanisms underlying primate ovarian aging at single-cell resolution, revealing new diagnostic biomarkers and potential therapeutic targets for age-related human ovarian disorders. Expression of this gene is highest in primordial oocytes.//////////////////
Expression regulated by
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Ovarian localization
Oocyte
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Effect of aging on mitochondria and metabolism of bovine granulosa cells. Nagata S et al. (2020) This study investigated the effect of aging on mitochondria in granulosa cells (GCs) collected from the antral follicles of young and aged cows (25-50 months and over 140 months in age, respectively). When GCs were cultured under 20% O2 for 4 days, mitochondrial DNA copy number (Mt-number), determined by real-time PCR, increased throughout the culture period, and the extent of increase was greater in the GCs of young cows than in those of old cows. In a second experiment, GCs were cultured under 20% O2 for 24 h. Protein levels of TOMM20 and TFAM in GCs were lower in aged cows than in young cows, and the amount of reactive oxygen species and the mitochondrial membrane potential were higher, whereas ATP content and proliferation activity were lower, respectively. Glucose consumption and lactate production were higher in the GCs of aged cows than in those of young cows. When GCs were cultured under 5% or 20% O2 for 24 h, low O2 decreased ATP content and increased glucose consumption in GCs of both age groups compared with high O2; however, low O2 decreased the Mt-number only in the GCs of young cows. In conclusion, we show that aging affects mitochondrial quantity, function, and response to differential O2 tensions in GCs.//////////////////