FIG. 2.

Genetic characterization of Acinetobacter hca genes associated with hydroxycinnamate catabolism. The newly discovered hca genes extend downstream from pobA in the dca-pca-qui-pob-hca cluster. As described here, HcaG hydrolyzes chlorogenate to quinate and caffeate. Metabolism of quinate to protocatechuate requires the qui genes, and HcaC initiates caffeate catabolism by converting the compound to its thioester. Upstream from hcaC and translated in the same direction is a 486-bp segment of an open reading frame encoding an aldehyde dehydrogenase. The complete open reading frame (hcaB) and an open reading frame designated hcaA have been shown in a separate study (Parke, unpublished) to encode genes for functions that complete the conversion of caffeate to protocatechuate. The locations of mutations used to identify functions of hca genes are indicated, as are the locations of plasmid inserts and restriction sites that were used for genetic construction.