YjbH-enhanced proteolysis of Spx by ClpXP in Bacillus subtilis is inhibited by the small protein YirB (YuzO)

Sushma Kommineni, Saurabh K. Garg, Chio Mui Chan, Peter Zuber

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20 Scopus citations


The Spx protein of Bacillus subtilis is a global regulator of the oxidative stress response. Spx concentration is controlled at the level of proteolysis by the ATP-dependent protease ClpXP and a substrate-binding protein, YjbH, which interacts with Spx. A yeast two-hybrid screen was carried out using yjbH as bait to uncover additional substrates or regulators of YjbH activity. Of the several genes identified in the screen, one encoded a small protein, YirB (YuzO), which elevated Spx concentration and activity in vivo when overproduced from an isopropyl-β-D-thiogalactopyranoside (IPTG)-inducible yirB construct. Pulldown experiments using extracts of B. subtilis cells producing a His-tagged YirB showed that native YjbH interacts with YirB in B. subtilis. Pulldown experiments using affinity-tagged Spx showed that YirB inhibited YjbH interaction with Spx. In vitro, YjbH-mediated proteolysis of Spx by ClpXP was inhibited by YirB. The activity of YirB is similar to that of the antiadaptor proteins that were previously shown to reduce proteolysis of a specific ClpXP substrate by interacting with a substrate-binding protein.

Original languageEnglish (US)
Pages (from-to)2133-2140
Number of pages8
JournalJournal of bacteriology
Issue number9
StatePublished - May 2011
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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