TSFM is a mitochondrial translation elongation factor. It is an enzyme that catalyzes the exchange of guanine nucleotides on the translation elongation factor Tu during the elongation step of mitchondrial protein translation. Mutations in TSFM are associated with combined oxidative phosphorylation deficiency-3 syndrome. Alternate splicing results in multiple transcript variants. Recombinant human TSFM protein, fused to His-tag at N-terminus, was expressed in E.coli.