Molecular insights into the m-AAA protease-mediated dislocation of transmembrane helices in the mitochondrial inner...

Area of Science:

• Mitochondrial biology
• Proteostasis
• Membrane protein processing

Background:

• The mitochondrial inner membrane houses vital protein complexes for cellular functions.
• The m-AAA protease, a hetero-hexameric AAA+ protease (Yta10/Yta12), maintains mitochondrial proteostasis.
• Its role in dislocating membrane-embedded substrates, including transmembrane segments, is poorly understood.

Purpose of the Study:

• To investigate the specific roles of transmembrane (TM) domains in the m-AAA protease function.
• To elucidate the mechanism of membrane-embedded substrate recognition and dislocation.
• To understand how TM domain alterations affect m-AAA protease activity.

Main Methods:

• Systematic replacement of individual TM domains in yeast m-AAA protease subunits (Yta10 and Yta12).
• Assessing the impact of TM domain mutations on membrane dislocation of various substrates.
• Analyzing the effect of substrate features, like downstream hydrophilic moieties, on dislocation efficiency.

Main Results:

• Replacement of Yta10 TM2 domain partially impaired membrane dislocation for specific substrates.
• Replacement of Yta12 TM2 domain significantly hindered membrane dislocation for all tested substrates.
• Large downstream hydrophilic moieties on substrates prevented m-AAA protease-mediated membrane dislocation, suggesting lipidic translocation.

Conclusions:

• TM domains of m-AAA protease subunits exhibit distinct functional roles in substrate recognition and dislocation.
• Yta12 TM2 domain is crucial for broad substrate dislocation, while Yta10 TM2 has a more specific role.
• Membrane dislocation likely occurs within the lipid bilayer, with limitations for bulky hydrophilic domains.