Promoter analysis of the staphylococcal enterotoxin A gene

The promoter region of the staphylococcal enterotoxin A (SEA) gene (sea) of Staphylococcus aureus was localized by primer extension analysis in conjunction with in vitro mutagenesis. The 5'-end of sea mRNA was located 86 base pairs upstream of the translational initiation codon. A DNA region with good agreement with canonical promoter sequences was observed beginning 8 base pairs upstream of the apparent transcriptional start site. Analysis of a series of progressive deletions of upstream DNA revealed that no DNA upstream of the putative -35 region was required for transcription of sea (determined by primer extension analysis) or for SEA production as detected by Western immunoblot analysis. Deletion mutants extending into the -35 region or mutants containing nucleotide substitutions in the -10 region both showed dramatic reductions in SEA production and transcription of sea. Analysis of a deletion mutant in which 59 base pairs between the transcriptional and translational start sites were deleted revealed slightly increased levels of SEA production.