Nucleotide sequence of the Acinetobacter calcoaceticus trpGDC gene cluster

A plasmid library of Acinetobacter calcoaceticus HindIII fragments wasconstructed, and clones that complemented an Escherichia coli pabA mutantwere selected. Plasmids containing a 3.9-kb fragment of A. calcoaceticusDNA that also complemented E. coli trpD and trpC-(trpF+) mutants wereobtained. We infer that complementation of E. coli pabA mutants was theresult of the expression of the amphibolic anthranilate-synthase/p-aminobenzoate-synthase glutamine-amidotransferase gene and thatthe plasmid insert carried the entire trpGDC gene cluster. In E. coliminicells, the plasmid insert directed the synthesis of polypeptides of44,000, 33,000, and 20,000 daltons, molecular masses that are consistentwith the reported molecular masses of phosphoribosylanthranilatetransferase, indoleglycerol-phosphate synthase, and anthranilate-synthasecomponent II, respectively. A 3,105- bp nucleotide sequence was determined.Comparison of the A. calcoaceticus trpGDC sequences with other known trpgene sequences has allowed insight into (1) the evolution of the amphibolictrpG gene, (2) varied strategies for coordinate expression of trp genes,and (3) mechanisms of gene fusions in the trp operon.