Cloning and nucleotide sequence of the type E staphylococcal enterotoxin gene

The gene for staphylococcal enterotoxin type E (entE) was cloned from Staphylococcus aureus into plasmid vector pBR322 and introduced into Escherichia coli. A staphylococcal enterotoxin type E-producing E. coli strain was isolated. The complete nucleotide sequence of the cloned structural entE gene and the N-terminal amino acid sequence of mature staphylococcal enterotoxin type E were determined. The entE gene contained 771 base pairs that encoded a protein with a molecular weight of 29,358 which was apparently processed to a mature extracellular form with a molecular weight of 26,425. DNA sequence comparisons indicated that staphylococcal enterotoxins type E and A are closely related. There was 84% nucleotide sequence homology between entE and the gene for staphylococcal enterotoxin type A; these genes encoded protein products that had 214 (83%) homologous amino acid residues (mature forms had 188 82% homologous amino acid residues).