A Human Mitochondrial Ferritin Encoded by an Intronless Gene

Iron is an abundant transition metal that is essential for life, being associated to many enzyme and oxygen carrier proteins involved in a variety of fundamental cellular processes. At the same time the metal is potentially toxic due to its capacity to engage in the catalytic production of noxious reactive oxygen species. The control of iron availability in the cells is largely dependent on ferritins, ubiquitous proteins with storage and detoxification capacity. In mammals, cytosolic ferritins are composed of two types of subunits, the H and the L chain, assembled to form a 24-mer spherical cage. Ferritin is present also in mitochondria, in the form of a complex with 24 identical chains. Even though the proteins have been known for a long time, their study is a very active and interesting field yet. In this review we will focus our attention to mammalian cytosolic and mitochondrial ferritins, describing the most recent advancement regarding their storage and antioxidant function, the effects of their genetic mutations in human pathology, and also the possible involvement in non-iron related activities. We will also discuss recent evidence connecting ferritins and the toxicity of iron in a set of neurodegenerative disorder characterized by focal cerebral siderosis. IntroductionThe adaptation of life to an oxic environment required the development of mechanisms to deal with the transformation of the water soluble ferrous ion (Fe 2+ ) to the insoluble ferric ion (Fe 3+ ) and with the concomitant generation of dangerous reactive oxygen species (ROS). The ferritin molecules represent an important and ancient mean developed by organisms in the three domains of life to safely handle the necessary, yet potentially toxic metal. Their ability to detoxify and store the metal through safe oxidation processes protects the cells from undue iron-dependent redox chemistry, while a controlled release of the metal guarantees its availability for different and essential enzymatic reactions. Storage and detoxification of iron represent the main functions of these molecules, and much work has been done to understand the chemical and molecular details of this

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“…Recently a mitochondrial ferritin (FtMt) has been identified (Levi et al 2001). It is encoded by an intronless gene at human chromosome 5q23.1.…”

Section: Mitochondrial Ferritinmentioning

confidence: 99%

Biology of ferritin in mammals: an update on iron storage, oxidative damage and neurodegeneration

2014

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“…Interestingly, mitochondrial ferritin is mainly comprised of H-chains (Levi et al, 2001, Santambrogio et al, 2007 which might indicate that the main function of this particular ferritin is to ensure that no Fe(II) is present, which in light of the substantial production of superoxide in mitochondria would make sense and prevent Fenton-type reactions. An overview of selected proteins and their function in iron metabolism is presented in Table 1.…”

Section: Systemic Iron Homeostasismentioning

confidence: 99%

The role of lysosomes in iron metabolism and recycling

Kurz

Eaton

Brunk

2011

The International Journal of Biochemistry & Cell Biology

172

134

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Iron is the most abundant transition metal in the earths crust. It cycles easily between ferric (oxidized; Fe(III)) and ferrous (reduced; Fe(II)) and readily forms complexes with oxygen, making this metal a central player in respiration and related redox processes. However, loose iron, not within heme or iron-sulfur cluster proteins, can be destructively redox-active, causing damage to almost all cellular components, killing both cells and organisms. This may explain why iron is so carefully handled by aerobic organisms. Iron uptake from the environment is carefully limited and carried out by specialized iron transport mechanisms. One reason that iron uptake is tightly controlled is that most organisms and cells cannot efficiently excrete excess iron. When even small amounts of intracellular free iron occur, most of it is safely stored in a non-redox-active form in ferritins. Within nucleated cells, iron is constantly being recycled from aged iron-rich organelles such as mitochondria and used for construction of new organelles. Much of this recycling occurs within the lysosome, an acidic digestive organelle. Because of this, most lysosomes contain relatively large amounts of redox-active iron and are therefore unusually susceptible to oxidant-mediated destabilization or rupture. In many cell types, iron transit through the lysosomal compartment can be remarkably brisk. However, conditions adversely affecting lysosomal iron handling (or oxidant stress) can contribute to a variety of acute and chronic diseases. These considerations make normal and abnormal lysosomal handling of iron central to the understanding and, perhaps, therapy of a wide range of diseases

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“…Iron is also an important cofactor in a class of enzymes using oxo-bridged binuclear iron centers. The ferroxidase center in mitochondrial ferritin contains a diiron carboxylate center (Levi et al 2001). A related site is present in the alternative oxidase (AOX) found in the mitochondrial respiratory chain of plants and some fungi (Maxwell et al 1999).…”

Section: Metal Ions Usage Within Mitochondriamentioning

confidence: 99%