The Spo0A sof mutations reveal regions of the regulatory domain that interact with a sensor kinase and RNA polymerase

Mol Microbiol. 1999 Jan;31(2):597-607. doi: 10.1046/j.1365-2958.1999.01200.x.


Spo0A is a two-domain response regulator required for the initiation of sporulation in Bacillus subtilis. Spo0A is activated by phosphorylation of its regulatory domain by a multicomponent phosphorelay. To define the role of the regulatory domain in the activation of Spo0A, we have characterized four of the sof mutations in vitro. The sof mutations were identified previously as suppressors of the sporulation-negative phenotype resulting from a deletion of the gene for one of the phosphorelay components, spo0F. Like wild-type Spo0A, the transcription stimulation properties of all of the Sof proteins were dependent upon phosphorylation. Sof mutants from two classes were improved substrates for direct phosphorylation by the KinA sensor kinase, providing an explanation for their suppression properties. Two other Sof proteins showed a phosphorylation-dependent enhancement of the stability of the Sof approximately P-RNA polymerase-DNA complex. One of these mutants, Sof114, increased the stability of the Sof114 approximately P-RNAP-DNA complex without increasing its own affinity for the spoIIG promoter. A comparison of the location of the sof mutations with mutations in CheY suggests that phosphorylation of Spo0A results in the exposure of a region in the regulatory domain that interacts with RNA polymerase, thereby contributing to the signal transduction mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / genetics
  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • DNA-Directed RNA Polymerases / metabolism*
  • Mutation*
  • Phosphoric Monoester Hydrolases / metabolism
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Sigma Factor / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcription, Genetic


  • Bacterial Proteins
  • Sigma Factor
  • Spo0A protein, Bacillus subtilis
  • Transcription Factors
  • kinA protein, Bacillus subtilis
  • spoIIR protein, Bacillus subtilis
  • spore-specific proteins, Bacillus
  • sporulation-specific sigma factors
  • Protein Kinases
  • DNA-Directed RNA Polymerases
  • Phosphoric Monoester Hydrolases