Multiple pathways of Spx (YjbD) proteolysis in Bacillus subtilis

Shunji Nakano, Guolu Zheng, Michiko Nakano, Peter Zuber

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

ATP-dependent proteases degrade denatured or misfolded proteins and are recruited for the controlled removal of proteins that block activation of regulatory pathways. Among the ATP-dependent proteases, those of the Clp family are particularly important for the growth and development of Bacillus subtilis. Proteolytic subunit ClpP, together with regulatory ATPase subunit ClpC or ClpX, is required for the normal response to stress, for development of genetic competence, and for sporulation. The spx (formally yjbD) gene was previously identified as a site of mutations that suppress defects in competence conferred by clpP and clpX. The level of Spx in wild-type cells grown in competence medium is low, and that in clpP mutants is high. This suggests that the Spx protein is a substrate for ClpP-containing proteases and that accumulation of Spx might be partly responsible for the observed pleiotropic phenotype resulting from the clpP mutation. In this study we examined, both in vivo and in vitro, which ClpP protease is responsible for degradation of Spx. Western blot analysis showed that Spx accumulated in clpX mutant to the same level as that observed in the clpP mutant. In contrast, a very low concentration of Spx was detected in a clpC mutant. An in vitro proteolysis experiment using purified proteins demonstrated that Spx was degraded by ClpCP but only in the presence of one of the ClpC adapter proteins, MecA or YpbH. However, ClpXP, either in the presence or in the absence of MecA and YpbH, was unable to degrade Spx. Transcription of spx, as measured by expression of spx-lacZ, was slightly increased by the clpX mutation. To exclude a possible effect of clpX and clpP on spx transcription, the spx gene was placed under the control of the IPTG (isopropyl-β-D-thiogalactopyranoside)-inducible Pspac promoter. In this strain, Spx accumulated when ClpX or ClpP was absent, suggesting that ClpX and ClpP are required for degradation of Spx. Taken together, these results suggest that Spx is degraded by both ClpCP and ClpXP. The putative proteolysis by ClpXP might require another adapter protein. Spx probably is degraded by ClpCP under as yet unidentified conditions. This study suggests that the level of Spx is tightly controlled by two different ClpP proteases.

Original languageEnglish (US)
Pages (from-to)3664-3670
Number of pages7
JournalJournal of Bacteriology
Volume184
Issue number13
DOIs
StatePublished - 2002

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Bacillus subtilis
Proteolysis
ATP-Dependent Proteases
Mental Competency
Proteins
Peptide Hydrolases
Mutation
Thiogalactosides
Growth and Development
Genes
Adenosine Triphosphatases
Western Blotting
Phenotype

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Immunology

Cite this

Multiple pathways of Spx (YjbD) proteolysis in Bacillus subtilis. / Nakano, Shunji; Zheng, Guolu; Nakano, Michiko; Zuber, Peter.

In: Journal of Bacteriology, Vol. 184, No. 13, 2002, p. 3664-3670.

Research output: Contribution to journalArticle

Nakano, Shunji ; Zheng, Guolu ; Nakano, Michiko ; Zuber, Peter. / Multiple pathways of Spx (YjbD) proteolysis in Bacillus subtilis. In: Journal of Bacteriology. 2002 ; Vol. 184, No. 13. pp. 3664-3670.
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