Structure and function of complex I in animals and plants – a comparative view
2017
Senkler, Jennifer | Senkler, Michael | Braun, Hans‐Peter
The mitochondrial NADH dehydrogenase complex (complex I) has a molecular mass of about 1000 kDa and includes 40–50 subunits in animals, fungi and plants. It is composed of a membrane arm and a peripheral arm and has a conserved L‐like shape in all species investigated. However, in plants and possibly some protists it has a second peripheral domain which is attached to the membrane arm on its matrix exposed side at a central position. The extra domain includes proteins resembling prokaryotic gamma‐type carbonic anhydrases. We here present a detailed comparison of complex I from mammals and flowering plants. Forty homologous subunits are present in complex I of both groups of species. In addition, five subunits are present in mammalian complex I, which are absent in plants, and eight to nine subunits are present in plant complex I which do not occur in mammals. Based on the atomic structure of mammalian complex I and biochemical insights into complex I architecture from plants we mapped the species‐specific subunits. Interestingly, four of the five animal‐specific and five of the eight to nine plant‐specific subunits are localized at the inner surface of the membrane arm of complex I in close proximity. We propose that the inner surface of the membrane arm represents a workbench for attaching proteins to complex I, which are not directly related to respiratory electron transport, like nucleoside kinases, acyl‐carrier proteins or carbonic anhydrases. We speculate that further enzyme activities might be bound to this micro‐location in other groups of organisms.
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