The Escherichia coli fmt gene, encoding methionyl-tRNA(fMet) formyltransferase, escapes metabolic control.
The genetic organization near the recently cloned fmt gene, encoding Escherichia coli methionyl-tRNA(fMet) formyltransferase (J. M. Guillon, Y. Mechulam, J. M. Schmitter, S. Blanquet, and G. Fayat, J. Bacteriol. 174:4294-4301, 1992), has been studied. The fmt gene, which starts at a GUG codon, is cotranscribed with another gene, fms, and the transcription start site of this operon has been precisely mapped. Moreover, the nucleotide sequence of a 1,379-bp fragment upstream from fmt reveals two additional open reading frames, in the opposite polarity. In the range of 0.3 to 2 doublings per h, the intracellular methionyl-tRNA(fMet) formyltransferase concentration remains constant, providing, to our knowledge, the first example of a gene component of the protein synthesis apparatus escaping metabolic control. When the gene fusion technique was used for probing, no effect on fmt expression of the concentrations of methionyl-tRNA(fMet) formyltransferase or tRNA(fMet) could be found. The possibility that the fmt gene, the product of which is present in excess to ensure full N acylation of methionyl-tRNA(fMet), could be expressed in a constitutive manner is discussed.
Meinnel
T
T
Laboratoire de Biochimie, Centre National de la Recherche Scientifique, Palaiseau, France.
Guillon
J M
JM
Mechulam
Y
Y
Blanquet
S
S
D000217:Acyltransferases / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003062:Codon; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D019877:Hydroxymethyl and Formyl Transferases; D008969:Molecular Sequence Data; D009239:N-Formylmethionine / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010442:Peptide Chain Initiation, Translational; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012358:RNA, Transfer, Met
D003062:Codon; D004269:DNA, Bacterial; D009838:Oligodeoxyribonucleotides; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; C024988:tRNA, formylmethionine-; D009239:N-Formylmethionine; D019877:Hydroxymethyl and Formyl Transferases; C021561:methionyl-tRNA formyltransferase; D000217:Acyltransferases