Functional and composition differences between mitochondrial complex II in Arabidopsis and rice are correlated with the complex genetic history of the enzyme |
| |
Authors: | Shaobai Huang Nicolas L Taylor Reena Narsai Holger Eubel James Whelan A Harvey Millar |
| |
Institution: | (1) ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, M316, Crawley, WA, 6009, Australia; |
| |
Abstract: | Complex II plays a central role in mitochondrial metabolism as a component of both the electron transport chain and the tricarboxylic
acid cycle. However, the composition and function of the plant enzyme has been elusive and differs from the well-characterised
enzymes in mammals and bacteria. Herewith, we demonstrate that mitochondrial Complex II from Arabidopsis and rice differ significantly
in several aspects: (1) Stability—Rice complex II in contrast to Arabidopsis is not stable when resolved by native electrophoresis
and activity staining. (2) Composition—Arabidopsis complex II contains 8 subunits, only 7 of which have homologs in the rice
genome. SDH 1 and 2 subunits display high levels of amino acid identity between two species, while the remainder of the subunits
are not well conserved at a sequence level, indicating significant divergence. (3) Gene expression—the pairs of orthologous
SDH1 and SDH2 subunits were universally expressed in both Arabidopsis and rice. The very divergent genes for SDH3 and SDH4 were co-expressed in both species, consistent with their functional co-ordination to form the membrane anchor. The plant-specific
SDH5, 6 and 7 subunits with unknown functions appeared to be differentially expressed in both species. (4) Biochemical regulation -succinate-dependent
O2 consumption and SDH activity of isolated Arabidopsis mitochondria were substantially stimulated by ATP, but a much more minor
effect of ATP was observed for the rice enzyme. The ATP activation of succinate-dependent reduction of DCPIP in frozen-thawed
and digitonin-solubilised mitochondrial samples, and with or without the uncoupler CCCP, indicate that the differential ATP
effect on SDH is not via the protonmotive force but likely due to an allosteric effect on the plant SDH enzyme itself, in
contrast to the enzyme in other organisms. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|