Mammalian mitochondrial methionyl-tRNA transformylase from bovine liver. Purification, characterization, and gene structure.
The mammalian mitochondrial methionyl-tRNA transformylase (MTFmt) was partially purified 2,200-fold from bovine liver mitochondria using column chromatography. The polypeptide responsible for MTFmt activity was excised from a sodium dodecyl sulfate-polyacrylamide gel and the amino acid sequences of several peptides were determined. The cDNA encoding bovine MTFmt was obtained and its nucleotide sequence was determined. The deduced amino acid sequence of the mature form of MTFmt consists of 357 amino acid residues. This sequence is about 30% identical to the corresponding Escherichia coli and yeast mitochondrial MTFs. Kinetic parameters governing the formylation of various tRNAs were obtained. Bovine MTFmt formylates its homologous mitochondrial methionyl-tRNA and the E. coli initiator methionyl-tRNA (Met-tRNAfMet) with essentially equal efficiency. The E. coli elongator methionyl-tRNA (Met-tRNAmMet) was also formylated although with somewhat less favorable kinetics. These results suggest that the substrate specificity of MTFmt is not as rigid as that of the E. coli MTF which clearly discriminates between the bacterial initiator and elongator Met-tRNAs. These observations are discussed in terms of the presence of a single tRNAMet gene in mammalian mitochondria.
Takeuchi
N
N
Department of Chemistry and Biotechnology, School of Engineering, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan.
Kawakami
M
M
Omori
A
A
Ueda
T
T
Spremulli
L L
LL
Watanabe
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology; D019877:Hydroxymethyl and Formyl Transferases / Q000737:chemistry*; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D001426:Bacterial Proteins; D010446:Peptide Fragments; D019877:Hydroxymethyl and Formyl Transferases; C021561:methionyl-tRNA formyltransferase