Sequence diversity and conservation in factors influencing succinate dehydrogenase flavinylation.

The mitochondrial enzyme succinate dehydrogenase (SDH) consists of four subunits, a flavoprotein (SDH1), an iron-sulfur (Fe-S) protein (SDH2) and two integral membrane subunits (SDH3/SDH4). In mammals and yeast, an assembly factor termed SDHAF2/SDH5 is required for accumulation of flavinylated SDH1. In Arabidopsis, we have recently reported the characterization of an unknown function protein with low sequence similarity to SDHAF2 that is needed for assembly and activity of SDH and also for normal root elongation. (1) In this short communication, we have reviewed the sequence diversity and conservation of SDHAF2 across kingdoms based on phylogenetic analysis. Given that flavinylation of SDH is dependent on the SDH1:SDHAF2 interaction, we have also discussed the conservation of the C-terminal tail of SDH1, which is required for this interaction process. In combination, we provide comparative evidence for a conserved role of SDHAF2 as an assembly factor from animals to plants.