Structural basis for distinct operational modes and protease activation in AAA+ protease Lon

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• AAA+ protein translocases utilize ATP hydrolysis for substrate translocation.
• Distinct conformational states of AAA+ proteases are suggested by biochemical data.
• The full conformational landscape of these enzymes remains incompletely understood.

Purpose of the Study:

• To elucidate the distinct operational modes of the Yersinia pestis Lon AAA+ protease.
• To uncover the structural basis for substrate-dependent conformational changes.
• To define the mechanistic principles of Lon protease plasticity.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine protein structures.
• Structures were solved for the Lon protease in both the absence and presence of substrate.
• Comparative structural analysis revealed distinct conformational states.

Main Results:

• In the absence of substrate, Lon adopts a left-handed, "open" spiral conformation with autoinhibited active sites.
• Upon substrate binding, Lon reorganizes into a right-handed, "closed" conformation with active protease sites.
• Two distinct operational modes were identified, driven by substrate presence.

Conclusions:

• The Yersinia pestis Lon AAA+ protease exhibits significant conformational plasticity.
• Substrate binding induces a switch from an inactive to an active conformation.
• These findings provide mechanistic insights into the processing of diverse protein substrates by AAA+ proteases.