The T. bruceiTRM5 methyltransferase plays an essential role in mitochondrial protein synthesis and function

Alfonzo and colleagues show that in the parasitic protist Trypanosoma brucei, a tRNA anticodon-loop guanosine base methylation affects translation differentially in mitochondria versus the cytoplasm. Mitochondrial protein synthesis is particularly sensitized. The anticodon-loop guanosine methylation was not required for tRNA import to mitochondria. Instead, the methyltransferase TRM5 is imported. Inhibition of expression of TRM5 and the resulting loss of anticodon-loop guanosine methylation greatly affected mitochondrially encoded protein synthesis and protist growth.