Molecular Biology and Evolution, Vol 3, 436-448, Copyright © 1986 by Society for Molecular Biology and Evolution
IP Crawford and L Eberly
We have determined the DNA sequence of the distal 148 codons of trpE and
all of trpG in Pseudomonas aeruginosa. These genes encode, respectively,
the large and small (glutamine amidotransferase) subunits of anthranilate
synthase, the first enzyme in the tryptophan synthetic pathway. The
sequenced region of trpE is homologous with the distal portion of E. coli
and Bacillus subtilis trpE, whereas the trpG sequence is homologous to the
glutamine amidotransferase subunit genes of a number of bacterial and
fungal anthranilate synthases. The two coding sequences overlap by 23 bp.
Codon usage in these Pseudomonas genes shows a marked preference for codons
ending in G or C, thereby resembling that of trpB, trpA, and several other
chromosomal loci from this species and others with a high G + C content in
their DNA. The deduced amino acid sequence for the P. aeruginosa trpG gene
product differs to a surprising extent from the directly determined amino
acid sequence of the glutamine amidotransferase subunit of P. putida
anthranilate synthase (Kawamura et al. 1978). This suggests that these two
proteins are encoded by loci that duplicated much earlier in the phylogeny
of these organisms but have recently assumed the same function. We have
also determined 490 bp of DNA sequence distal to trpG but have not
ascertained the function of this segment, though it is rich in dyad
symmetries.
ORIGINAL ARTICLE
Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: I. Sequence of trpG encoding the glutamine amidotransferase subunit
Department of Microbiology, University of Iowa, Iowa City 52242.
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