A subcomplex of human mitochondrial RNase P is a bifunctional methyltransferase – extensive moonlighting in mitochondrial tRNA biogenesis

摘要

In 2012, we reported that all three human TRM10 homologues have tRNA methyltransferase activity. However, in a recent follow-up study, we were not able to reproduce the reported tRNA:m1G9 methyltransferase activity of human TRMT10B with fresh enzyme preparations. This prompted us to revisit the original preparation used in 2012, and mass spectrometry analysis of the concerned TRMT10B preparation revealed a significant contamination with TRMT10A, suggesting that the tRNA:m1G9 methyltransferase activity previously observed was in fact due to TRMT10A rather than TRMT10B. The contamination was not previously noticed, because the two recombinant proteins have a similar molecular weight and were therefore not resolved by SDS-PAGE.