Activation of the extracytoplasmic function σ factor σ^V by lysozyme

Area of Science:

• Microbiology
• Bacterial Physiology
• Signal Transduction

Background:

• Sigma V (σ^V) is an extracytoplasmic function (ECF) σ factor found in Firmicutes, crucial for lysozyme resistance.
• Its activity is regulated by the anti-σ factor RsiV, a transmembrane protein that also acts as a lysozyme receptor.

Purpose of the Study:

• To elucidate the mechanism of σ^V activation in response to lysozyme.
• To investigate the role of RsiV degradation in the activation cascade.

Main Methods:

• Analysis of the RsiV degradation pathway.
• Identification of the protease responsible for site-1 cleavage of RsiV.
• Lysozyme-dependent assays to study RsiV cleavage and σ^V activation.

Main Results:

• Lysozyme binding to RsiV initiates a signal transduction cascade leading to RsiV degradation.
• Site-1 cleavage of RsiV is performed by a constitutively active signal peptidase in a lysozyme-dependent manner.
• Activated σ^V drives the transcription of genes essential for lysozyme resistance.

Conclusions:

• The σ^V-RsiV system provides a specific mechanism for lysozyme resistance in Firmicutes.
• Signal peptidase plays a unique, lysozyme-regulated role in activating ECF σ factors.
• Understanding this pathway offers insights into bacterial defense mechanisms against cell wall-degrading enzymes.