Adaptor bypass mutations of Bacillus subtilis spx suggest a mechanism for YjbH‐enhanced proteolysis of the regulator Spx by ClpXP. Issue 3 (10th July 2014)

• Record Type: Journal Article
• Authors: Chan, Chio Mui; Hahn, Erik; Zuber, Peter
• Is Part Of: Molecular microbiology. Volume 93:Issue 3(2014)
• Page Start: 426
• Page End: 438
• Publication Date: 2014-07-10
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.12671
• Languages: English
• ISSNs: 0950-382X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>The global regulator, Spx, is under proteolytic control exerted by the adaptor YjbH and ATP‐dependent protease ClpXP in <italic>B</italic><italic>acillus subtilis</italic>. While YjbH is observed to bind the Spx C‐terminus, YjbH shows little affinity for ClpXP, indicating adaptor activity that does not operate by tethering. Chimeric proteins derived from <italic>B</italic><italic>. subtilis</italic> AbrB and the Spx C‐terminus showed that a 28‐residue C‐terminal section of Spx (AbrB28), but not the last 12 or 16 residues (AbrB12, AbrB16), was required for YjbH interaction and for ClpXP proteolysis, although the rate of AbrB28 proteolysis was not affected by YjbH addition. The result suggested that the YjbH‐targeted 28 residue segment of the Spx C‐terminus bears a ClpXP‐recognition element(s) that is hidden in the intact Spx protein. Residue substitutions in the conserved helix α6 of the C‐terminal region generated Spx substrates that were degraded by ClpXP at accelerated rates compared to wild‐type Spx, and showed reduced dependency on the YjbH activity. The residue substitutions also weakened the interaction between Spx and YjbH. The results suggest a model in which YjbH, through interaction with residues of helix α6, exposes the C‐terminus of Spx for recognition and proteolysis by ClpXP.</p> </abstract>