Structure and function of complex I in animals and plants - a comparative view.

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Respiration

Background:

• Mitochondrial NADH dehydrogenase (complex I) is a large enzyme complex crucial for cellular respiration.
• Complex I has a conserved structure across eukaryotes but exhibits variations, especially in plants.
• Plant complex I possesses an additional peripheral domain with potential novel functions.

Purpose of the Study:

• To compare the subunit composition of complex I between mammals and flowering plants.
• To identify species-specific subunits and map their locations within the complex.
• To investigate the functional implications of these species-specific subunits.

Main Methods:

• Comparative analysis of complex I subunit composition in mammals and plants.
• Utilizing atomic structures of mammalian complex I and biochemical data from plants.
• Mapping of species-specific subunits onto the complex I structure.

Main Results:

• Complex I in mammals and plants shares 40 homologous subunits.
• Mammalian complex I has five unique subunits, while plant complex I has eight to nine unique subunits.
• Many species-specific subunits are localized to the inner surface of the membrane arm.

Conclusions:

• The inner surface of the complex I membrane arm acts as a platform for attaching non-respiratory proteins.
• Plant-specific subunits, including carbonic anhydrases, are associated with this platform.
• This suggests complex I may integrate additional enzymatic activities beyond electron transport.