DEFORMYLATION AND PROTEIN BIOSYNTHESIS

An enzyme which removes formyl groups from N-formylmethionylaminoacyl-transfer ribonucleic acid and its chemically synthesized analog, N-formylmethionylpuromycin, has been prepared from extracts of Escherichia coli. The specificity of the enzyme is that expected of a deformylase active during protein biosynthesis. It fails to act upon N-formylmethione or N-formylmethionyl-transfer ribonucleic acid until the blocked amino acid is transferred into an initial intermediate of protein synthesis, N-formylmethionylaminoacyl-transfer ribonucleic acid. The critical role of the formyl blocking group prior to the formation of the initial peptide bond and its presumed redundancy thereafter are consistent with this specificity. As previously demonstrated and confirmed in these studies, the enzyme also deformylates free formyl peptides. In addition, the differences observed in N terminals of in vitro and in vivo synthesized E. coli and certain bacteriophage proteins are likely accounted for by the marked lability of the enzyme in crude and purified extracts. Both SO42-and SO32-increase the initial reaction rate of the enzyme, but neither of these anions nor a variety of other compounds prevent the enzyme’s rapid in vitro inactivation. Following the removal of the formyl blocking group, N-terminal methionine is removed by an aminopeptidase present in these preparations, a reaction required by the nature of the N-terminal residues of many bacterial and ribonucleic acid viral proteins. © 1969, American Chemical Society. All rights reserved.