Multiple domains of bacterial and human Lon proteases define substrate selectivity

Area of Science:

• Biochemistry
• Molecular Biology
• Protease Function

Background:

• The Lon protease degrades proteins in prokaryotes and eukaryotes.
• Mechanisms for normal protein substrate selection by Lon protease are poorly understood.

Purpose of the Study:

• To identify novel Lon protease substrates.
• To investigate the organism-specific substrate selection of Lon protease.

Main Methods:

• Identification of F. tularensis Lon substrates.
• Cross-species degradation assays using human and bacterial Lon variants.
• Domain swapping experiments between human and bacterial Lon proteases.
• In vitro proteolysis and mass spectrometry analysis.

Main Results:

• Ten new F. tularensis Lon substrates were identified.
• Human Lon protease could not degrade many bacterial Lon substrates, indicating organism-specific selection.
• Replacing individual domains of human Lon did not confer bacterial substrate degradation ability.
• Lon proteases exhibit similar substrate cleavage patterns, favoring hydrophobic amino acids at the P(-1) site.

Conclusions:

• Lon protease substrate selection is organism-adapted and involves multiple domains.
• Structural matching between Lon protease and its substrates contributes to substrate specificity.