TRANSCRIPTIONAL REGULATION OF THE YERSINIA-PSEUDOTUBERCULOSIS PH-6 ANTIGEN ADHESIN BY 2 ENVELOPE-ASSOCIATED COMPONENTS

The Yersinia pseudotuberculosis pH 6 antigen mediates haemagglutinatio n and adhesion to cultured mammalian cells. The synthesis of pH 6 anti gen requires the products of the psaEFABC genes in both Yersinia pseud otuberculosis and Escherichia coli. In-frame deletion mutations of psa E and psaF caused defective haemagglutination. In contrast, we showed that the psaABC genes were sufficient for haemaggrutination if they we re expressed by a heterologous promoter. Environmental regulation of p H 6 antigen by temperature and pH occurs via regulation of the major p ilus protein PsaA at the transcriptional level. Northern blot analyses indicate that the psaA transcript was absent in either psaE or psaF m utant strains. Primer extension analyses indicate that, in Y. pseudotu berculosis, the transcription of the psaE and psaF genes is constituti ve. Alkaline phosphatase fusion studies confirm the topology predictio n that PsaE and PsaF are both inner-membrane-associated proteins. PsaE consists of an N-terminal cytoplasmic domain, containing sequence sim ilarity to transcriptional regulators found in two-component systems a s well as to the Salmonella typhimurium HilA protein, with a C-termina l domain that is periplasmically localized. PsaF is predicted to be or iented with most of the protein in the periplasm, the hydrophobic N-te rminus being either integrated in the inner membrane or cleaved as a s ignal peptide.