Cloning, sequence analysis and expression of mammalian mitochondrial protein synthesis elongation factor Tu

The bovine liver mitochondrial protein synthesis elongation factor Tu.Ts complex (EF-TU.Tsmt) has been purified and partial peptide sequence information has been obtained for EF-Tumt. A complete cDNA has been obtained encoding bovine EF-Tumt and a nearly complete cDNA has been obtained for human EF-Tumt. The bovine cDNA has a 5' untranslated leader, an open reading frame of 1356 nucleotides and a 3' untranslated region of 189 base pairs. NH2-terminal sequencing of the mature protein indicates that the transit peptide for the mitochondrial localization of this protein is 43 amino acids in length. The human and bovine factors are 95% identical. The deduced protein sequences show considerable identity to bacterial and organellar EF-Tu sequences. At least two genes for EF-Tumt are present in the bovine system. Northern analysis indicates that EF-Tumt is synthesized in all tissues but that the level of expression varies over a wide range. EF-TUmt has been expressed in E. coli as a His-tagged protein and purified to near homogeneity. The expressed form of the factor is active in the poly(U)-directed polymerization of phenylalanine although it is less active than the native EF-Tu.Tsmt complex.