Structure, function, and assembly of heme centers in mitochondrial respiratory complexes

Area of Science:

• Biochemistry
• Cell Biology
• Bioenergetics

Background:

• Mitochondrial respiratory chain facilitates sequential electron flow using redox cofactors.
• Heme groups, alongside flavins, iron-sulfur, and copper, are key prosthetic groups in complexes II, III, and IV.
• The precise role of heme b in complex II remains less understood compared to complexes III and IV.

Purpose of the Study:

• To detail the functions of hemes in mitochondrial respiratory complexes.
• To elucidate the role of hemes in electron transfer and complex assembly.
• To review the current understanding of heme involvement in complexes II, III, and IV.

Main Methods:

• Literature review of studies on mitochondrial respiratory complexes.
• Analysis of the structural and functional roles of hemes.
• Examination of heme's impact on complex assembly processes.

Main Results:

• Heme b in complex III bifurcates electron flow from ubiquinol oxidation.
• Heme c in Cyt1 transfers electrons to peripheral cytochrome c.
• Heme a(3)/Cu(B) site in complex IV catalyzes oxygen reduction.
• Heme absence impairs complex II assembly in mammalian cells.
• Heme attachment is vital for complex III and IV assembly and proper protein folding.

Conclusions:

• Heme groups are essential for both catalytic activity and assembly of mitochondrial respiratory complexes.
• Understanding heme's role in assembly is crucial for comprehending mitochondrial function.
• Further research is needed to fully detail heme's function, especially in complex II.