Processing of the N termini of nascent polypeptide chains requires deformylation prior to methionine removal.
N-formyl-methionine termini are formed in the initiation reaction of bacterial protein synthesis and processed during elongation of the nascent polypeptide chain. We report that the formyl group must be removed before the methionine residue can be cleaved by methionine aminopeptidase. This has long been implicitly assumed, but that assumption was based on inconclusive data and was in apparent conflict with more recently published data. We demonstrate that the Salmonella typhimurium methionine aminopeptidase is totally inactive on an N-formyl-methionyl peptide in vitro, and present a detailed characterization of the substrate specificity of this key enzyme by use of a very sensitive and quantitative assay. Finally, a reporter protein expressed in a strain lacking peptide deformylase was shown to retain the formyl group confirming the physiological role of the deformylase.
Solbiati
J
J
Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
Chapman-Smith
A
A
Miller
J L
JL
Miller
C G
CG
Cronan
J E
JE
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000378:metabolism*; D005561:Formates / Q000378:metabolism*; D007700:Kinetics; D008715:Methionine / Q000378:metabolism*; D063208:Methionyl Aminopeptidases; D010449:Peptide Mapping; D011499:Protein Processing, Post-Translational; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
D005561:Formates; C030544:formic acid; D008715:Methionine; D000626:Aminopeptidases; D063208:Methionyl Aminopeptidases