Related Experiment Videos
Protein substrates and heat shock reduce the DNA-binding ability of Escherichia coli Lon protease
1Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu, Japan.
Abstract:
Interaction between the fusion protein MBP-Lon, formed by maltose-binding protein and Lon protease, and the plasmid pBR322 was studied to clarify the DNA-binding behavior of the Lon protease. Since the MBP-Lon fusion protein that was bound to the plasmid was strongly adsorbed by amylose resin, complex formation and dissociation were determined by quantifying the unadsorbed plasmid using agarose gel electrophoresis. The autolysis of MBP-Lon fusion protein was suppressed when the protein was bound to the plasmid. The plasmid was completely dissociated from MBP-Lon fusion protein by the addition of the protein substrates of Lon protease (i.e. alpha-casein and denatured bovine serum albumin). In addition, at high temperatures, MBP-Lon fusion protein lost its plasmid-binding ability, although it fully retained ATP-dependent protease activity. These results suggest that Lon protease loses DNA-binding ability when cells are exposed to abnormal conditions and the amount of damaged proteins increases. On the other hand, DNA probably plays an important role in controlling the Lon protease activity in cells under normal conditions by entrapping the enzyme.
Insights
The Lon protease, a fusion protein, binds to plasmid DNA, which suppresses its self-degradation. This DNA binding is lost under cellular stress, suggesting a role in regulating protease activity.
Area of Science:
- Molecular Biology
- Biochemistry
- Enzymology
Background:
- The Lon protease is an ATP-dependent serine protease involved in protein degradation.
- Its interaction with DNA is not fully understood, particularly its role in cellular regulation.
Purpose of the Study:
- To investigate the DNA-binding behavior of the Lon protease.
- To clarify the relationship between DNA binding, protease activity, and cellular conditions.
Main Methods:
- Utilized a fusion protein (MBP-Lon) for studying DNA interaction.
- Employed amylose resin for complex adsorption and agarose gel electrophoresis for quantification.
- Assessed autolysis suppression and dissociation using protein substrates and temperature variations.
Main Results:
- MBP-Lon fusion protein binds to plasmid pBR322 DNA, suppressing its autolysis.
- DNA binding is reversed by Lon protease substrates (alpha-casein, denatured BSA).
- High temperatures abolish DNA binding but retain protease activity.
Conclusions:
- Lon protease loses DNA-binding ability under cellular stress (high temperature, increased damaged proteins).
- DNA likely regulates Lon protease activity under normal conditions by sequestering the enzyme.
- This interaction suggests a mechanism for controlling protease function based on cellular state.