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J. Bacteriol., 09 1997, 5935-5942, Vol 179, No. 18
PA Williams and LE Shaw
Benzyl alcohol, benzaldehyde, benzoate, and anthranilate are metabolized
via catechol, cis,cis-muconate, and the beta-ketoadipate pathway in
Acinetobacter calcoaceticus ADP1 (BD413). Mutant strain ISA25 with a
deletion spanning catBCIJF and unable to metabolize muconate further will
not grow in the presence of an aromatic precursor of muconate. Growth on
fumarate as the sole carbon source with added benzyl alcohol or
benzaldehyde selected spontaneous mutants of ISA25. After repair of the cat
deletion by natural transformation with linearized plasmid pPAN4 (catBCIJF)
10 mutants were unable to grow on benzoate of cis,cis-muconate but could
still grow on anthranilate. Transformation with wild-type chromosomal DNA
demonstrated the presence of two unlinked mutations in each strain, one in
the benABCD region, encoding the conversion of benzoate to catechol, and
the other in a gene determining the ability to grow on exogenous
cis,cis-muconate. The wild-type gene, named mucK, was cloned into pUC18,
and its nucleotide sequence was determined. It encodes a 413-residue
protein of M(r) = 45,252 which is a member of a superfamily of membrane
transport proteins and which is within a subgroup involved in the uptake of
organic acids. Five of the mutant alleles were cloned, and the mutations
were determined by nucleotide sequencing. All the mutations were in the
mucK coding region and consisted of three deletions, one duplication, and a
substitution. Insertional inactivation of mucK resulted in the loss of the
ability to utilize exogenous muconate. The location of mucK on the
chromosome appeared to be unique for genes associated with the benzoate
branch of the beta-ketoadipate pathway in being close to the pca-qui-pob
gene cluster (for p-hydroxybenzoate utilization) and distant from the
functionally related ben-cat cluster. Downstream of mucK and transcribed in
the same direction is an open reading frame encoding a protein of 570
residues (M(r) = 63,002) which shows considerable homology with a mammalian
electron transport protein; its insertional inactivation had no detectable
phenotypic effect.
Copyright © 1997, American Society for Microbiology
mucK, a gene in Acinetobacter calcoaceticus ADP1 (BD413), encodes the ability to grow on exogenous cis,cis-muconate as the sole carbon source
School of Biological Sciences, University of Wales, Bangor, Gwynedd, United Kingdom. P.A.Williams@Bangor.ac.uk
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