Cytochrome c

Cytochrome c is a small heme protein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins and plays a major role in cell apoptosis and the electron transport chain.

Structure

Cytochrome c has a primary structure consisting of a chain of about 100 amino acids. Many amino acids in cytochrome c are post-translationally modified, in a process called isomerization. The protein has a secondary structure which folds into a compact tertiary structure, due to the heme group which is attached to the protein.

Function

Cytochrome c plays a key role in the electron transport chain, in the third stage of cellular respiration. It accepts electrons from the bc1 complex and transfers them to the cytochrome c oxidase complex. In addition, cytochrome c is also involved in initiation of apoptosis. Upon release of cytochrome c to the cytoplasm, the protein binds Apaf-1 and ATP, which then bind procaspase-9 to create a protein complex known as an apoptosome.

Clinical significance

Alterations in the structure or function of cytochrome c can lead to a variety of diseases, including cancer, neurodegenerative diseases, and cardiovascular diseases. For example, mutations in cytochrome c can disrupt the function of the electron transport chain, leading to a buildup of reactive oxygen species and cell damage.

See also

• Electron transport chain
• Apoptosis
• Mitochondrion

References

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