CLONING AND EXPRESSION OF MITOCHONDRIAL TRANSLATIONAL ELONGATION-FACTOR TS FROM BOVINE AND HUMAN LIVER

The sequences of the cDNAs for the mitochondrial translational elongation factor Ts (EF-Ts(mt)) from bovine and human liver have been obtained. The deduced amino acid sequence of bovine liver EF-Ts(mt) is 338 residues in length and includes a 55-amino acid signal peptide and a mature protein of 283 residues. The sequence of the mature form of bovine EF-Ts(mt) is 91% identical to that of human EF-Ts(mt) and 29% identical to Escherichia coli EF-Ts. Southern analysis indicates that there are two genes for EF-Ts(mt) in bovine liver chromosomal DNA. A 224-base pair intron is located near the 5'-end of at least one of these genes. Northern analysis using a human multiple tissue blot indicates that EF-Ts(mt) is expressed in all tissues, with the highest levels of expression in skeletal muscle, liver, and kidney. Both the mature and precursor forms of bovine liver EF-Ts(mt) have been expressed in E. coli as histidine-tagged pro teins, The mature form of EF-Ts(mt) forms a complex with E. coli elongation factor Tu. This complex is active in poly(U) directed polymerization of phenylalanine. The precursor form is expressed as a 42-kDa protein, which is rapidly degraded in the cell.