Bovine complex I is a complex of 45 different subunits
Joe Carroll1, Ian M Fearnley, J Mark Skehel
1Dunn Human Nutrition Unit, The Medical Research Council, Hills Road, Cambridge CB2 2XY, United Kingdom.
The Journal of Biological Chemistry
|September 5, 2006
Summary
Researchers identified a 46th subunit in bovine mitochondrial complex I. This previously suspected component is actually a fragment of subunit SGDH, clarifying the complex's protein composition.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Respiration
Background:
- Mammalian mitochondrial complex I is a large, multisubunit protein complex essential for cellular respiration.
- Previous studies characterized 45 subunits, but a 46th was suspected based on mass spectrometry data.
Purpose of the Study:
- To definitively characterize the suspected 46th subunit of bovine mitochondrial complex I.
- To establish the complete protein subunit composition of bovine mitochondrial complex I.
Main Methods:
- Electrospray ionization mass spectrometry (ESI-MS) of fractionated subunits.
- Tandem mass spectrometry (MS/MS) of intact protein ions.
- Chromatographic analysis to resolve subunits.
Main Results:
- A 46th component with a mass of 10,566 Da was detected.
- This component was found associated with the intact complex and subcomplex Ibeta.
- Tandem mass spectrometry revealed it to be a C-terminal fragment of subunit SGDH, resulting from a specific peptide bond cleavage during ESI-MS.
Conclusions:
- Bovine mitochondrial complex I consists of 45 distinct protein subunits.
- The previously suspected 46th subunit is an artifact of the mass spectrometry process, specifically a fragment of SGDH.
- The complete composition of bovine mitochondrial complex I, including FMN and iron-sulfur clusters, is now established.
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