Molecular and General Genetics MGG

, Volume 249, Issue 5, pp 474–486

SlyA, a regulatory protein from Salmonella typhimurium, induces a haemolytic and pore-forming protein in Escherichia coli

Authors

  • Albrecht Ludwig
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
  • Claudia Tengel
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
  • Susanne Bauer
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
  • Andreas Bubert
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
  • Roland Benz
    • Theodor-Boveri-Institut, BiotechnologieBiozentrum der Universität Würzburg
  • Hans-Joachim Mollenkopf
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
  • Werner Goebel
    • Theodor-Boveri-Institut, MikrobiologieBiozentrum der Universität Würzburg
Original Paper

DOI: 10.1007/BF00290573

Cite this article as:
Ludwig, A., Tengel, C., Bauer, S. et al. Molec. Gen. Genet. (1995) 249: 474. doi:10.1007/BF00290573

Abstract

A chromosomal fragment from Salmonella typhimurium, when cloned in Escherichia coli, generates a haemolytic phenotype. This fragment carries two genes, termed slyA and slyB. The expression of slyA is sufficient for the haemolytic phenotype. The haemolytic activity of E. coli carrying multiple copies of slyA is found mainly in the cytoplasm, with some in the periplasm of cells grown to stationary phase, but overexpression of SlyB, a 15 kDa lipoprotein probably located in the outer membrane, may lead to enhanced, albeit unspecific, release of the haemolytic activity into the medium. Polyclonal antibodies raised against a purified SlyA-HlyA fusion protein identified the over-expressed monomeric 17 kDa SlyA protein mainly in the cytoplasm of E. coli grown to stationary phase, although smaller amounts were also found in the periplasm and even in the culture supernatant. However, the anti-SlyA antibodies reacted with the SlyA protein in a periplasmic fraction that did not contain the haemolytic activity. Conversely, the periplasmic fraction exhibiting haemolytic activity did not contain the 17 kDa SlyA protein. Furthermore, S. typhimurium transformed with multiple copies of the slyA gene did not show a haemolytic phenotype when grown in rich culture media, although the SlyA protein was expressed in amounts similar to those in the recombinant E. coli strain. These results indicate that SlyA is not itself a cytolysin but rather induces in E. coli (but not in S. typhimurium) the synthesis of an uncharacterised, haemolytically active protein which forms pores with a diameter of about 2.6 nm in an artificial lipid bilayer. The SlyA protein thus seems to represent a regulation factor in Salmonella, as is also suggested by the similarity of the SlyA protein to some other bacterial regulatory proteins. slyA- and slyB-related genes were also obtained by PCR from E. coli, Shigella sp. and Citrobacter diversus but not from several other gram-negative bacteria tested.

Key words

Salmonella typhimuriumSlyAVirulence factorRegulation of gene expressionEscherichia coliHaemolysin

Copyright information

© Springer-Verlag 1995