Human METTL20 is a Mitochondrial Lysine Methyltransferase that Targets the Beta Subunit of Electron Transfer Flavoprotein (ETF{beta}) and Modulates Its Activity [Bioenergetics]

November 21st, 2014 by Malecki, J., Ho, A. Y. Y., Moen, A., Dahl, H.-A., Falnes, P. O.

ABSTRACT Proteins are frequently modified by post-translational methylation of lysine residues, catalyzed by S-adenosylmethionine (SAM) dependent lysine (K) methyltransferases (KMTs). Lysine methylation of histone proteins has been extensively studied, but it has recently become evident that methylation of non-histone proteins is also abundant and important. The human methyltransferase (MTase) METTL20 belongs to a group of ten established and putative human KMTs. We here found METTL20 to be associated with mitochondria, and that recombinant METTL20 methylated a single protein in extracts from human cells. Using an MTase activity-based purification scheme, we identified the β-subunit of the mitochondrially localized electron transfer flavoprotein (ETFβ) as the substrate of METTL20. Furthermore, METTL20 was found to specifically methylate two adjacent lysine residues, K200 and K203, in ETFβ both in vitro and in cells. Interestingly, the residues methylated by METTL20 partially overlap with the so-called recognition-loop in ETFβ, which has been shown to mediate its interaction with various dehydrogenases. Accordingly, we found that METTL20-mediated methylation of ETFβ in vitro reduced its ability to receive electrons from the medium chain acyl-CoA dehydrogenase (MCAD) and the glutaryl-CoA dehydrogenase (GCDH). In conclusion, the present study establishes METTL20 as the first human KMT localized to mitochondria, and suggests that it may regulate cellular metabolism through modulating the interaction between its substrate ETF and dehydrogenases. Based on the previous naming of similar enzymes, we suggest the renaming of human METTL20 to ETFβ-KMT.
  • Posted in Journal of Biological Chemistry, Publications
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