
Mutagenesis of a 30-bp bidirectional fragment. Bases essential for promoter activity in each direction are underlined. Transversion mutations were introduced three bases at a time and shifted two bases for a total of 15 mutants. Mutation of a 12-bp region annihilates promoter activity in both directions. The consensus CCGGAARYR is recognized by the transcription factor GABPA. Asterisks (*) indicate position of transcription start sites.











