iron ion transmembrane transport

Definition

Target type: biologicalprocess

A process in which an iron ion is transported from one side of a membrane to the other by means of some agent such as a transporter or pore. [GOC:mah, PMID:11390404]

Iron ion transmembrane transport is a crucial biological process that ensures the delivery of iron, an essential element for numerous cellular functions, across cell membranes. This intricate process involves a coordinated interplay of specialized membrane proteins, specific transport mechanisms, and regulatory factors.

Iron, a transition metal, plays a vital role in diverse cellular processes, including:

* **Oxygen transport:** Hemoglobin, the protein responsible for oxygen transport in red blood cells, requires iron as a key component.
* **Electron transport chain:** Iron-containing proteins, such as cytochromes and iron-sulfur clusters, participate in the electron transport chain, facilitating energy production through cellular respiration.
* **DNA synthesis and repair:** Iron is essential for the function of enzymes involved in DNA replication and repair.
* **Immune function:** Iron is crucial for the production and activity of immune cells, such as lymphocytes and macrophages.

However, iron, in its free form, can be highly toxic, leading to the generation of reactive oxygen species (ROS) that damage cellular components. To maintain iron homeostasis and prevent toxicity, cells have evolved sophisticated mechanisms to regulate iron uptake, storage, and efflux.

**Iron Ion Transmembrane Transport Mechanisms**

**1. Iron Uptake:**

* **Transferrin-mediated endocytosis:** The primary mechanism for iron uptake in most cells involves transferrin, a plasma protein that binds iron in the bloodstream. Transferrin binds to its receptor (TfR) on the cell surface, and the complex is internalized through endocytosis. Once inside the cell, iron is released from transferrin in acidic endosomes and transported to the cytoplasm.
* **Non-transferrin-bound iron (NTBI) uptake:** Cells can also take up iron that is not bound to transferrin. This pathway is less efficient than transferrin-mediated uptake and may involve membrane transporters such as Zrt/Irt-like protein (ZIP) family members.

**2. Iron Storage:**

* **Ferritin:** Ferritin is the major intracellular iron storage protein. It sequesters iron in a safe and readily available form, preventing iron toxicity.
* **Hemosiderin:** Hemosiderin is another iron storage protein that forms when iron is in excess. It is less soluble and more difficult to mobilize than ferritin.

**3. Iron Efflux:**

* **Ferroportin:** Ferroportin is the primary iron exporter protein. It transports iron out of cells into the bloodstream, where it can be bound to transferrin and delivered to other tissues.
* **Hephaestin:** Hephaestin is a copper-dependent ferroxidase that oxidizes ferrous iron (Fe2+) to ferric iron (Fe3+), facilitating its transport by ferroportin.

**Regulation of Iron Ion Transmembrane Transport**

* **Hepcidin:** Hepcidin is a key regulator of iron homeostasis. It is a hormone produced by the liver that binds to ferroportin, leading to its internalization and degradation, thereby reducing iron efflux from cells.
* **Iron Regulatory Proteins (IRP):** IRPs are cytoplasmic proteins that bind to iron-responsive elements (IREs) in the 5' untranslated region (UTR) of mRNAs involved in iron metabolism. IRPs regulate the translation of these mRNAs in response to iron availability.
* **Other factors:** Several other factors, including hypoxia, inflammation, and erythropoiesis, also contribute to the regulation of iron ion transmembrane transport.

**Disorders Related to Iron Ion Transmembrane Transport**

* **Iron deficiency anemia:** This is the most common nutritional deficiency worldwide. It occurs when iron intake is insufficient or iron absorption is impaired, leading to reduced iron availability for hemoglobin synthesis.
* **Hemochromatosis:** This is a genetic disorder characterized by excessive iron absorption and accumulation in the body. It can damage various organs, including the liver, heart, and pancreas.
* **Acanthocytosis:** This is a rare genetic disorder caused by mutations in the gene encoding the transferrin receptor. It is characterized by red blood cells with irregular, thorny projections.

**Conclusion**

Iron ion transmembrane transport is a vital process that ensures the proper balance of iron within the body. It involves intricate interactions between membrane proteins, transport mechanisms, and regulatory factors. Dysregulation of iron transport can lead to various disorders, highlighting the importance of maintaining iron homeostasis for overall health.'
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Proteins (2)

Compounds (5)