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Fig. 2 | Journal of Cardiothoracic Surgery

Fig. 2

From: Myocardial insufficiency is related to reduced subunit 4 content of cytochrome c oxidase

Fig. 2

The subunit composition of the human ‘heart-type’ cytochrome c oxidase in 2D- gelelectrophoresis according to the Kadenbach- classification. Present study is focused on subunit 2 and 4 (arrows). CytOx from mammals and birds is composed of 13 subunits. The three catalytic subunits 1–3 are encoded by mitochondrial DNA, while 10 are nuclear-encoded. The latter ones are essentially involved in the regulation of oxygen consumption and proton translocation, since their removal or modification changes the activity and while their mutations may lead to mitochondrial diseases. Respiration is differently regulated in organs and species by expression of tissue-, developmental-, and species-specific isoforms for COX subunits 4, 6a, 6b, 7a, 7b, and 8, but the holoenzyme in mammals is always composed of 13 subunits [8]. Essential for the assembly and the oxygen consumption of the enzyme is the subunit 4 [9]. In the text, the subunits are termed in arabic numbers while mitochondrial enzyme complexes of the ETC are termed in latin numbers

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