The DNA encoding the exfoliative toxin A gene (eta) of Staphylococcus aureus was cloned into bacteriophage Xgtll and subsequently into plasmid pLI50 on a 1,391-base-pair DNA fragment of the chromosome. Exfoliative toxin A is expressed in the Escherichia coli genetic background, is similar in length to the toxin purified from culture medium, and is biologically active in an animal assay. The nucleotide sequence of the DNA fragment containing the gene was determined. The protein deduced from the nucleotide sequence is a polypeptide of 280 amino acids. The mature protein is 242 amino acids. The DNA sequence of the exfoliative toxin B gene was also determined. Corrections indicate that the amino acid sequence of exfoliative toxin B is in accord with chemical sequence data.The exfoliative toxins A and B (ETA and ETB) of Staphylococcus aureus are the causative agents of staphylococcal scalded-skin syndrome (11). They possess the same biological activity (12), but they are immunologically distinct proteins (11, 12). The two forms also differ in amino acid composition, amino acid sequence, and heat resistance (13). In addition, eta is expressed from the chromosome, whereas etb is of plasmid origin (14,21,29).To study the mode of action and the molecular properties of these two proteins, we set out to clone and sequence both genes. Recently, we reported the cloning and sequencing of the etb gene (9, 10). In this communication, we report the cloning and DNA sequence of eta. O'Toole and Foster (17) also reported the cloning of eta and in the accompanying paper (18) report their sequence of the gene. Our data and their report contain identical DNA sequence determinations as well as general conclusions regarding the expression of the eta gene. eta is expressed in the Escherichia coli background and is biologically active in the neonatal mouse assay. Furthermore, the sequence of the protein deduced from the DNA sequence is identical to the published sequence of the N-terminal region of the ETA molecule (12). MATERIALS AND METHODSBacterial strains and plasmids. S. aureus UT0002, a phage group II staphylococcal scalded-skin syndrome clinical isolate (20), was used as the source of library DNA. E. coli Y1090 was used in the Protoclone system (Promega Biotec Co., Madison, Wis.) as a recipient for bacteriophage Xgtll packaging carried out according to the manufacturer's instructions. E. coli LE392 was used for transformation and propagation of plasmids and cloned DNA (16).* Corresponding author.