STRUCTURE AND TRANSCRIPTIONAL REGULATION OF THE ESCHERICHIA-COLI ADAPTIVE RESPONSE GENE AIDB

Expression of the Escherichia coli aidB gene is induced in vivo by alk ylation damage in an ada-dependent pathway and by anaerobiosis or by a cetate at pH 6.5 in an ada-independent fashion. In this report, we pre sent data on aidB gene structure, function, and regulation. The aidB g ene encodes a protein of ca. 60 kDa that is homologous to;several mamm alian acyl coenzyme A dehydrogenases. Accordingly, crude extracts from an aidB-overexpressing strain showed isovaleryl coenzyme A dehydrogen ase activity. aidB overexpression also reduced N-methyl-N'-nitro-N-nit rosoguanidine-induced mutagenesis. Both ada- and acetate/pH-dependent induction of aidB are regulated at the transcriptional level, and the same transcriptional start point is used for both kinds of induction. Ada protein plays a direct role in aidB regulation: methylated Ada is able to bind to the aidB promoter region and to activate transcription from aidB in an in vitro transcription-translation system using crude E. coli extracts.