Identification of a lipoamide dehydrogenase gene as second locus affected in poly(3-hydroxybutyric acid)-leaky mutants of Alcaligenes eutrophus

From a genomic library of Alcaligenes eutrophus strain H16 in the broad-host range cosmid pVK100 a 6300-bp EcoRI-fragment was cloned, which restored the wild-type phenotype in transposon-induced poly(3-hydroxybutyric acid)-leaky mutants, derived from A. eutrophus. Nucleotide sequence analysis of the region adjacent to the transposon insertion revealed an open reading frame which complied with all criteria for a coding region. This region was referred to as phbL, and the deduced amino acid sequence from this part of phbL showed 60% amino acid identity in an overlap of 98 residues to the lipoamide dehydrogenase gene (lpd) of Escherichia coli. In addition, the 6300-bp EcoRI-fragment conferred expression of lipoamide dehydrogenase activity to E. coli.