| Abstract | Ubiquinol-cytochrome c reductase (bc1 complex or complex III) is an enzyme complex of bacterial and mitochondrial oxidative phosphorylation systems It catalyses the
oxidoreduction of the mobile redox components ubiquinol and cytochrome c, generating an
electrochemical potential, which is linked to ATP synthesis [ 2986972, 3004982].
The complex consists of three subunits in most bacteria, and nine in mitochondria: both
bacterial and mitochondrial complexes contain cytochrome b and cytochrome c1 subunits,
and an iron-sulphur `Rieske' subunit, which contains a high potential 2Fe-2S cluster [2820981].The mitochondrial form also includes six other subunits that do not
possess redox centres. Plastoquinone-plastocyanin reductase (b6f complex), present in
cyanobacteria and the chloroplasts of plants, catalyses the oxidoreduction of plastoquinol
and cytochrome f. This complex, which is functionally similar to ubiquinol-cytochrome c
reductase, comprises cytochrome b6, cytochrome f and Rieske subunits [1391772].
The Rieske subunit acts by binding either a ubiquinol or plastoquinol anion, transferring
an electron to the 2Fe-2S cluster, then releasing the electron to the cytochrome c or
cytochrome f haem iron [2986972, 1391772]. The rieske domain has a [2Fe-2S] centre. Two conserved cysteines that one Fe ion while the other Fe ion is coordinated by two conserved histidines. The 2Fe-2S cluster is bound in the
highly conserved C-terminal region of the Rieske subunit. |
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