Regulation of expression of the dadA gene encoding D-amino acid dehydrogenase in Escherichia coli: analysis of dadA-lac fusions and direction of dadA transcription.

The catabolism of most d-amino acids is carried out by d-amino dehydrogenase, coded by the dadA gene. Employing Mud(Aprlac) phage (Casadaban and Cohen 1979) the lac structural gene were fused to the control region of the dadA locus. Expression the of the lacZ gene in the dad-lac fusions was shown to be inducible by alanine and catabolite-repressible, thus responding to regulatory signals known to affect expression of the dadA gene. The method of MacNeil et al. (1980) was adopted to transfer the chromosomal dadA-lac fusion into lambda phage. By use of isolated lambda ddadA-lac1 phage, the promoter for the dadA gene was located, which enabled determination of the direction of dadA transcription as being counter-clockwise.