Biochemistry

Freedom to Associate

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Science  04 Mar 2005:
Vol. 307, Issue 5714, pp. 1377
DOI: 10.1126/science.307.5714.1377e

The power-generating capacity of mitochondria is based on redox reactions (in complexes I, II, III, and IV) that establish an electrochemical gradient of protons, which is used to make ATP (in complex V). The redox reactions utilize the mobile electron carriers ubiquinone and cytochrome C, and considerations of catalytic flux as well as sequestration of reactive intermediates (not to mention membrane morphology and integrity) have led to the view that these complexes might associate into supercomplexes. Dudkina et al. provide electron microscopic evidence that in plant mitochondria, a 1.5-megadalton conglomerate of complex I and dimeric complex III exists. This observation fits nicely with recent human genetics studies that have linked mutations in genes coding subunits in one mitochondrial complex with functional or structural deficiencies in another. — GJC

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.0408870102 (2005).

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