COMPLETE SEQUENCE AND ORGANIZATION OF THE SERRATIA-MARCESCENS BIOTIN OPERON

The nucleotide sequence of the biotin (bio) operon of wild-type Serrat ia marcescens Sr41 was determined. Five ORFs were identified to encode BioA (7,8-diaminopelargonic acid aminotransferase), BioB (biotin synt hase). BioF (7-keto-8-aminopelargonic acid synthase). BioC (an enzyme catalysing the synthesis of pimeloyl-CoA) and BioD (dethiobiotin synth ase). in this order. The operon was deduced to be transcribed divergen tly to the left into bioA and to the right into the bioBFCD genes. The promoters and a common predicted operator for both bioA and bioBFCD g enes were located between the bioA and bioB genes. The predicted amino acid sequences of these enzymes were similar to the sequences of the corresponding enzymes of Escherichia coil. Analysis of expression of t he lacZ structural gene fused with the bioA and blob promoters reveale d that the biotin operon was subject to biotin-mediated feedback repre ssion.