Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016719 (Friedreich's ataxia)
 2,098 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tim44 is an essential component of the mitochondrial inner membrane protein import machinery. In this study we asked if Tim44 is of relevance in intramitochondrial protein folding. We investigated the role of Tim44 in the biogenesis of the authentic mitochondrial protein Yfh1p, the yeast homolog of mammalian frataxin, which was recently implicated in Friedreich ataxia. After inactivation of Tim44, binding of mitochondrial heat shock protein (mtHsp)70 to translocating Yfh1p and subsequent folding to the native state was nearly completely blocked. Residual amounts of imported Yfh1p showed an increased tendency to aggregate. To further characterize the functions of Tim44 in the matrix, we imported dihydrofolate reductase (DHFR) as a model protein. Depletion of Tim44 allowed import of DHFR, although folding of the newly imported DHFR was delayed. Moreover, the depletion of Tim44 caused a strongly reduced binding of mtHsp70 and Mge1 to the translocating polypeptide. Subsequent dissociation of mtHsp70 from imported DHFR was delayed, indicating that mtHsp70-substrate complexes formed independently of Tim44 differ from the complexes that form under the control of Tim44. We conclude that Tim44 not only plays a role in protein translocation but also in the pathways of mitochondrial protein folding.
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PMID:Biogenesis of the yeast frataxin homolog Yfh1p. Tim44-dependent transfer to mtHsp70 facilitates folding of newly imported proteins in mitochondria. 1082 1

The human gene frataxin and its yeast homolog YFH1 affect mitochondrial function. Deficits in frataxin result in Friedreich ataxia, while deletion of YFH1 results in respiratory incompetence. We determined that as long as respiratory incompetent yeast express Yfh1p they do not accumulate excessive mitochondrial iron. Deletion of YFH1 in respiratory incompetent yeast results in mitochondrial iron accumulation, while the reintroduction of Yfh1p results in mitochondrial iron export. Further, overexpression of Yfh1p has no effect on oxygen consumption in wild-type yeast grown in either fermentative or respiratory carbon sources. We conclude that the effect of Yfh1p on mitochondrial iron metabolism is independent of respiratory activity.
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PMID:YFH1-mediated iron homeostasis is independent of mitochondrial respiration. 1173 20

The yeast ATM1 protein is essential for normal mitochondrial iron homeostasis. Deletion of ATM1 results in mitochondrial iron accumulation and oxidative mitochondrial damage. Mutations in ABC7, the human homolog of ATM1, result in X-linked sideroblastic anemia and ataxia. Here we show that a deletion of ATM1 also has effects on extra-mitochondrial iron metabolism. ATM1-deficient cells have an increased iron requirement for growth. When grown in iron-rich medium, mutant cells accumulate excess mitochondrial iron and have increased expression of the genes required for both high and low affinity iron uptake. Thus, ATM1 mutant cells simultaneously demonstrate features of both iron overload and iron starvation. Yfh1p is the yeast homolog of the human frataxin protein, which is deficient in Friedreich's ataxia. As in atm1 cells, a yfh1 deletion results in both mitochondrial iron accumulation and cytosolic iron starvation. In spite of their apparent roles in cellular iron homeostasis, we find that the expression of neither ATM1 nor YFH1 is responsive to cellular iron status. Based on these observations, we propose a model in which cellular iron is prioritized for use by the mitochondrion, and available to the remainder of the cell only after mitochondrial needs have been fulfilled.
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PMID:The role of the mitochondrion in cellular iron homeostasis. 1612 Feb 68