Subunit structures of purified beef mitochondrial cytochromebc 1 complex from liver and heart

Abstract

The existence of tissue-specific isozymes of cytochrome c oxidase has been widely documented. We have now studied if there are differences between subunits of mitochondrial bc1 complexes isolated from liver and heart. For this purpose, we have developed a method for the purification of an active ubiquinol-cytochrome c oxidoreductase from adult bovine liver that includes solubilization of submitochondrial particles with deoxycholate, ammonium acetate fractionation, resolubilization with dodecyl maltoside, and ion exchange chromatography. The electrophoretic pattern of the liver preparation showed the presence of 11 subunits, with apparent molecular weights identical to the ones reported for the heart complex. Western blot analysis and isoelectric focusing followed by two-dimensional gels of bc1 complexes from liver and heart were compared, and no qualitative differences were observed. In addition, the high-molecular-weight subunits of the purified complexes from both tissues, subunits I, II, V, and VI, were isolated by PAGE in the presence of Coomasie Blue and subjected to limited proteolysis and to chemical digestion with cyanogen bromide and BNPS-skatol, and the peptide patterns were compared. Finally, two of the small-molecular-weight subunits from the liver complex were isolated (subunits VII and X), partially analyzed by amino terminal sequencing, and found to be identical with the reported sequence of their heart counterparts. The data suggest that, in contrast to the case of cytochrome c oxidase, bc1 complexes from liver and heart do not exhibit tissue-specific differences.

Different Metabolic Properties of Mitochondrial Oxidative Phosphorylation in Different Cell Types ‐ Important Implications for Mitochondrial Cytopathies

“…In contrast, the IV-1 isoform is ubiquitously expressed (Hüttemann et al 2001). In contrast to the case of COX, cytochrome bc 1 complexes from bovine liver and heart do not exhibit tissue-specific differences (Vazquez-Acevedo et al 1993).…”

A Novel Syndrome Affecting Multiple Mitochondrial Functions, Located by Microcell-Mediated Transfer to Chromosome 2p14-2p13

“…Activity of the bc 1 complex was determined according to the method described by Darley-Usmar et al (1987). Western blotting was performed on mitochondrial extracts prepared by the method of Pitkä nen et al (1996), using polyclonal antibodies against (a) porcine-heart PDHcomplex raised in rabbit (Ekong 1982) and (b) holo bc 1 and iron-sulfur protein (ISP)-bc 1 bovine heart-and-liver complex raised in rabbit (Vazquez-Acevedo et al 1993).…”

Distinct Structures and Environments for the Three Hemes of the Cytochrome bc1Complex fromRhodospirillum rubrum. A Resonance Raman Study Using B-Band Excitations

“…Oligomeric electron-transfer enzymes containing a monoheme c-type cytochrome (cyt), a diheme cyt b, and a 2Fe-2S Rieske center are found in bacteria, chloroplasts, and mitochondria, and share many functional and structural properties ( − ). These membrane-bound proteins, named cyt bc 1 or cyt b 6 f complexes, are involved in respiration in eukaryotic cells or participate in respiration, photosynthesis, denitrification and/or nitrogen fixation in bacteria ( − ).…”