The pca-pob supraoperonic cluster of Acinetobacter calcoaceticus contains quiA, the structural gene for quinate-shikimate dehydrogenase.
An 18-kbp Acinetobacter calcoaceticus chromosomal segment contains the pcaIJFBDKCHG operon, which is required for catabolism of protocatechuate, and pobSRA, genes associated with conversion of p-hydroxybenzoate to protocatechuate. The genetic function of the 6.5 kbp of DNA between pcaG and pobS was unknown. Deletions in this DNA were designed by removal of fragments between restriction sites, and the deletion mutations were introduced into A. calcoaceticus by natural transformation. The mutations prevented growth with either quinate or shikimate, growth substrates that depend upon qui gene function for their catabolism to protocatechuate. The location of quiA, a gene encoding quinate-shikimate dehydrogenase, was indicated by its expression in one of the deletion mutants, and the position of the gene was confirmed by determination of its 2,427-bp nucleotide sequence. The deduced amino acid sequence of QuiA confirmed that it is a member of a family of membrane-associated, pyrrolo-quinoline quinone-dependent dehydrogenases, as had been suggested by earlier biochemical investigations. Catabolism of quinate and skikimate is initiated by NAD(+)-dependent dehydrogenases in other microorganisms, so it is evident that different gene pools were called upon to provide the ancestral enzyme for this metabolic step.
Elsemore
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Department of Biology, Yale University, New Haven, Connecticut 06520.
Ornston
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D016954:Acinetobacter calcoaceticus / Q000235:genetics*; D000429:Alcohol Oxidoreductases / Q000235:genetics*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016296:Mutagenesis; D009876:Operon; D011801:Quinic Acid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012765:Shikimic Acid / Q000378:metabolism*; D014170:Transformation, Genetic
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D011801:Quinic Acid; D012765:Shikimic Acid; D000429:Alcohol Oxidoreductases; C091165:QuiA protein, Acinetobacter calcoaceticus