MUCK, A GENE IN ACINETOBACTER-CALCOACETICUS ADP1 (BD413), ENCODES THEABILITY TO GROW ON EXOGENOUS CIS,CIS-MUCONATE AS THE SOLE CARBON SOURCE

Benzyl alcohol, benzaldehyde, benzoate, and anthranilate are metaboliz ed 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 w ill not grow in the presence of an aromatic precursor of muconate. Gro wth on fumarate as the sole carbon source with added benzyl alcohol or benzaldehyde selected spontaneous mutants of ISA25, After repair of t he cat deletion by natural transformation with linearized plasmid pPAN 4 (catBCIJF) 10 mutants were unable to grow on benzoate or cis,cis-muc onate but could still grow on anthranilate, Transformation with wild-t ype chromosomal DNA demonstrated the presence of two unlinked mutation s in each strain, one in the benABCD region, encoding the conversion o f benzoate to catechol, and the other in a gene determining the abilit y to grow on exogenous cis,cis-muconate, The wild-type gene, named muc K, 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 sub group involved in the uptake of organic acids, Five of the mutant alle les were cloned, and the mutations were determined by nucleotide seque ncing. All the mutations were in the mucK coding region and consisted of three deletions, one duplication, and a substitution, Insertional i nactivation of mucK resulted in the loss of the ability to utilize exo genous muconate. The location of mucK on the chromosome appeared to be unique for genes associated with the benzoate branch of the beta-keto adipate 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 direc tion 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 phen otypic effect.