Article

Bovine complex I is a complex of 45 different subunits.

Dunn Human Nutrition Unit, The Medical Research Council, Hills Road, Cambridge CB2 2XY, United Kingdom.
Journal of Biological Chemistry (impact factor: 4.77). 11/2006; 281(43):32724-7. DOI:10.1074/jbc.M607135200
Source: PubMed

ABSTRACT Mammalian mitochondrial complex I is a multisubunit membrane-bound assembly with a molecular mass approaching 1 MDa. By comprehensive analyses of the bovine complex and its constituent subcomplexes, 45 different subunits have been characterized previously. The presence of a 46th subunit was suspected from the consistent detection of a molecular mass of 10,566 by electrospray ionization mass spectrometry of subunits fractionated by reverse-phase high pressure liquid chromatography. The component was found associated with both the intact complex and subcomplex Ibeta, which represents most of the membrane arm of the complex, and it could not be resolved chromatographically from subunit SGDH (the subunit of bovine complex I with the N-terminal sequence Ser-Gly-Asp-His). It has now been characterized by tandem mass spectrometry of intact protein ions and shown to be a C-terminal fragment of subunit SGDH arising from a specific peptide bond cleavage between Ile-55 and Pro-56 during the electrospray ionization process. Thus, the subunit composition of bovine complex I has been established. It is a complex of 45 different proteins plus non-covalently bound FMN and eight iron-sulfur clusters.

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Keywords

45 different proteins
 
45 different subunits
 
bovine complex
 
C-terminal fragment
 
consistent detection
 
electrospray ionization mass spectrometry
 
electrospray ionization process
 
iron-sulfur clusters
 
Mammalian mitochondrial complex
 
molecular mass
 
multisubunit membrane-bound assembly
 
N-terminal sequence Ser-Gly-Asp-His
 
non-covalently
 
specific peptide bond cleavage
 
subunit SGDH
 
subunits fractionated
 
tandem mass spectrometry