Biomics

The bacterial tryptophan operon contains genes that code for the enzymes of tryptophan biosynthesis from chorismic acid. Although this operon is a classic example of how transcription is attenuated in the synthesis of the TrpL leader peptide, GenBank has only 215 trpL genes, of which 151 have been described in Escherichia and Salmonella. In this work, we compared the tryptophan operons of 20 strains from 7 families of the order Enterobacteriales. The structure of the enterobacterial operon was found to be conserved. The differences we detected were due either to the presence of a separate trpG gene in the operon or to the inclusion of the protein encoded by this gene as part of the TrpD bifunctional enzyme as a domain. For all strains examined – and for the first for 17 strains – analysis of the nucleotide sequences located before the operon’s first structural gene detected genes of the TrpL leader peptide. These peptides were 14 to 36 amino acids residues in length and contained between 1 (Pantoea agglomerans) and 5 (Vibrio cholerae) tryptophan residues. The TrpL peptides of most strains contained two tryptophan residues in neighboring positions. In individual enterobacterial genera and families, the TrpL structure was either conserved (within most genera and within the Enterobacteriaceae) or highly variable (within the genera Vibrio and Pantoea and within the families Erwiniaceae and Morganellaceae). Our results allow the conclusion that the programs available for whole genome data annotation (such as the RAST and NCBI Prokaryotic Genome Annotation Pipeline platform) may work incorrectly with respect to the detection of the leader peptides of bacterial tryptophan operons. Further, the results suggest the need for inclusion of information about leader peptides and their genes in the appropriate databases

enterobacteria; tryptophan operon; leader peptide; transcription attenuation; sequence annotation

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