Homocysteine thiolactone is a positive effector of sigma(S) levels in Escherichia coli

FEMS Microbiol Lett. 2000 Apr 15;185(2):117-21. doi: 10.1111/j.1574-6968.2000.tb09048.x.


sigma(S) is a regulator of the stationary phase response in Escherichia coli. Multi-copy suppressors were sought in a strain with decreased levels of sigma(S) and one such suppressor was found to encode HsrA, a putative efflux pump. Multi-copy expression of hsrA was shown to lead to accumulation of homocysteine, which is predicted to cause an increase in homocysteine thiolactone (HCTL) levels. A direct correlation between HCTL levels and sigma(S) accumulation was observed both in mutants and during normal cell growth, leading to the hypothesis that HCTL is a physiologically relevant positive effector of sigma(S) levels in vivo.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Culture Media
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial
  • Homocysteine / analogs & derivatives*
  • Homocysteine / metabolism
  • Methionine / metabolism
  • Repressor Proteins*
  • Sigma Factor / genetics
  • Sigma Factor / metabolism*
  • Vitamin B 12 / metabolism


  • Bacterial Proteins
  • Culture Media
  • Escherichia coli Proteins
  • Repressor Proteins
  • Sigma Factor
  • rspA protein, E coli
  • sigma factor KatF protein, Bacteria
  • Homocysteine
  • Methionine
  • homocysteine thiolactone
  • Vitamin B 12