Efficient expression and purification of biologically active human cystatin proteins

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Expression

Background:

• Cystatins are vital cysteine protease inhibitors regulating cathepsins, neurodegenerative diseases, and immune responses.
• Recombinant cystatin production is crucial for understanding their biochemical properties and functions.

Purpose of the Study:

• To clone and express human stefin A, stefin B, and cystatin C in Escherichia coli.
• To develop efficient purification strategies for these recombinant cystatins.
• To assess the biological activity of purified cystatins against specific proteases.

Main Methods:

• Gene cloning and expression in E. coli.
• Utilizing chaperone plasmids (Trigger factor, GroES-GroEL, DnaK-DnaJ-GrpE) to enhance soluble expression of cystatin C.
• Purification using immobilized metal affinity chromatography, glutathione sepharose, and anion exchange chromatography.
• Inhibition assays against cathepsin L and H3 protease.

Main Results:

• Successful cloning and expression of human stefin A, stefin B, and cystatin C in E. coli.
• Chaperone co-expression significantly improved the solubility of cystatin C, facilitating its recovery from the soluble fraction.
• Efficient purification protocols were established for all three cystatins.
• Inhibition assays demonstrated the biological activity of the purified proteins against target proteases.

Conclusions:

• Recombinant expression of human stefin A, stefin B, and cystatin C in E. coli is feasible.
• Chaperone-assisted expression is an effective strategy for overcoming solubility issues with cystatin C.
• The developed methods allow for the production of active cystatins for further research.