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Selectivity among Anti-σ Factors by Mycobacterium tuberculosis ClpX Influences Intracellular Levels of Extracytoplasmic Function σ Factors.

Abstract：

:Extracytoplasmic function σ factors that are stress inducible are often sequestered in an inactive complex with a membrane-associated anti-σ factor. Mycobacterium tuberculosis membrane-associated anti-σ factors have a small, stable RNA gene A (ssrA)-like degron for targeted proteolysis. Interaction between the unfoldase, ClpX, and a substrate with an accessible degron initiates energy-dependent proteolysis. Four anti-σ factors with a mutation in the degron provided a set of natural substrates to evaluate the influence of the degron on degradation strength in ClpX-substrate processivity. We note that a point mutation in the degron (X-Ala-Ala) leads to an order-of-magnitude difference in the dwell time of the substrate on ClpX. Differences in ClpX/anti-σ interactions were correlated with changes in unfoldase activities. Green fluorescent protein (GFP) chimeras or polypeptides with a length identical to that of the anti-σ factor degron also demonstrate degron-dependent variation in ClpX activities. We show that degron-dependent ClpX activity leads to differences in anti-σ degradation, thereby regulating the release of free σ from the σ/anti-σ complex. M. tuberculosis ClpX activity thus influences changes in gene expression by modulating the cellular abundance of ECF σ factors.IMPORTANCE The ability of Mycobacterium tuberculosis to quickly adapt to changing environmental stimuli occurs by maintaining protein homeostasis. Extracytoplasmic function (ECF) σ factors play a significant role in coordinating the transcription profile to changes in environmental conditions. Release of the σ factor from the anti-σ is governed by the ClpXP2P1 assembly. M. tuberculosis ECF anti-σ factors have an ssrA-like degron for targeted degradation. A point mutation in the degron leads to differences in ClpX-mediated proteolysis and affects the cellular abundance of ECF σ factors. ClpX activity thus synchronizes changes in gene expression with environmental stimuli affecting M. tuberculosis physiology.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Joshi AC,Kaur P,Nair RK,Lele DS,Nandicoori VK,Gopal B

doi

10.1128/JB.00748-18

subject

Has Abstract

pub_date

2019-02-25 00:00:00

issue

eissn

0021-9193

issn

1098-5530

pii

JB.00748-18

journal_volume

201

pub_type

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Selectivity among Anti-σ Factors by Mycobacterium tuberculosis ClpX Influences Intracellular Levels of Extracytoplasmic Function σ Factors.