Cyt c

Cytochrome c (Cyt c) is a small heme protein found loosely associated with the inner membrane of the mitochondrion. It is a component of the electron transport chain in mitochondria and plays a crucial role in the generation of ATP through oxidative phosphorylation. Cytochrome c is also involved in the process of apoptosis, or programmed cell death.

Structure

Cytochrome c is a highly conserved protein across different species, indicating its essential role in cellular processes. It consists of a single polypeptide chain with a heme group covalently attached. The heme group is responsible for the protein's ability to transfer electrons.

Function

Cytochrome c functions as an electron carrier in the electron transport chain. It transfers electrons between Complex III (Coenzyme Q - Cytochrome c reductase) and Complex IV (Cytochrome c oxidase) of the mitochondrial inner membrane. This transfer is a critical step in the process of oxidative phosphorylation, which ultimately leads to the production of ATP. In addition to its role in energy production, cytochrome c is involved in the intrinsic pathway of apoptosis. Upon receiving apoptotic signals, cytochrome c is released from the mitochondria into the cytosol, where it interacts with Apaf-1 and caspase-9 to form the apoptosome, leading to the activation of caspase-3 and the execution of apoptosis.

Role in Apoptosis

The release of cytochrome c from the mitochondria is a key event in the intrinsic pathway of apoptosis. This release is regulated by the Bcl-2 family of proteins, which includes both pro-apoptotic and anti-apoptotic members. Once in the cytosol, cytochrome c binds to Apaf-1, leading to the formation of the apoptosome and the subsequent activation of caspases, which are the executioners of apoptosis.

Clinical Significance

Dysregulation of cytochrome c release and function can lead to various diseases. For example, excessive release of cytochrome c can result in excessive cell death, contributing to neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. Conversely, insufficient release of cytochrome c can prevent the normal process of apoptosis, potentially leading to cancer.

Related Pages

• Mitochondrion
• Electron transport chain
• Oxidative phosphorylation
• Apoptosis
• Bcl-2 family
• Complex III (Coenzyme Q - Cytochrome c reductase)
• Complex IV (Cytochrome c oxidase)
• Apaf-1
• Caspase-9
• Caspase-3
• Neurodegenerative diseases
• Parkinson's disease
• Alzheimer's disease
• Cancer