Protein quality control and regulated proteolysis in the genome-reduced organism Mycoplasma pneumoniae

Area of Science:

• Cellular Biology
• Molecular Biology
• Microbiology

Background:

• Protein degradation is essential for cellular function and proteome homeostasis.
• Understanding minimal cellular machinery provides insights into fundamental biological processes.

Purpose of the Study:

• To define the minimal protein degradation machinery in Mycoplasma pneumoniae.
• To elucidate the specific roles of ATP-dependent proteases Lon and FtsH in proteostasis.

Main Methods:

• Conditional depletion of essential ATP-dependent proteases (Lon and FtsH).
• Shotgun proteomics and RNA-sequencing to identify protein substrates.
• Cellular localization studies and epistasis experiments.
• Protein half-life measurements.

Main Results:

• Depletion of Lon protease led to increased protein aggregation and reduced heat tolerance.
• Depletion of FtsH protease caused cell membrane damage, indicating a role in membrane protein quality control.
• Identified 62 Lon and 34 FtsH candidate substrates through integrated omics studies.
• Demonstrated distinct cellular functions for Lon and FtsH proteases.

Conclusions:

• Lon protease is crucial for degrading misfolded proteins and ensuring protein complex assembly, playing a key role in protein quality control.
• FtsH protease is involved in the quality control of membrane proteins.
• The coordinated action of proteases and chaperones maintains protein folding and degradation balance in minimal cells.
• Regulation of protein complex assembly and degradation by Lon and FtsH likely coordinates cellular processes such as cell division.