Characterization of a randomized FRET library for protease specificity determination

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Protease specificity determination is crucial for understanding enzyme function and developing new therapeutics.
• Genomic sequencing has revealed a vast number of proteases, necessitating high-throughput characterization methods.
• Existing methods for protease specificity determination can be slow and labor-intensive.

Purpose of the Study:

• To construct and characterize a novel protein-based Förster Resonance Energy Transfer (FRET) library for high-throughput protease specificity determination.
• To develop a sensitive and reliable method for identifying protease cleavage sites.
• To assess the utility of fluorescent proteins (GFP and DsRed) as components of protease substrates.

Main Methods:

• Construction of a FRET library using Green Fluorescent Protein (GFP) and DsRed, with a randomized oligonucleotide linker region between them.
• Generation of diverse protease substrates by incorporating a mixture of nucleotide bases at 27 positions within the linker.
• Kinetic assays monitoring GFP fluorescence increase to determine relative reaction velocities for various proteases.
• Colony screening using color development and restriction enzyme digests to remove non-functional DNA constructs (e.g., those with stop codons or deletions).

Main Results:

• The FRET library successfully generated diverse substrates with randomized amino acid sequences.
• Kinetic assays demonstrated the ability of tested proteases to discriminate between different substrates.
• The fluorescent proteins GFP and DsRed showed resistance to proteolysis, ensuring assay integrity.
• Screening methods effectively eliminated undesirable DNA constructs from the library.

Conclusions:

• The developed protein-based FRET library provides a sensitive, reliable, and high-throughput method for protease specificity determination.
• This approach facilitates the characterization of novel proteases identified through genomic efforts.
• The library design and screening strategy offer an efficient workflow for protease substrate discovery.