Optical determination of glutamine using a genetically engineered protein

Area of Science:

• Biochemistry
• Biotechnology
• Analytical Chemistry

Background:

• Glutamine is a crucial amino acid in cell metabolism and culture.
• Accurate monitoring of glutamine is essential for bioprocesses and research.
• Existing biosensors may have limitations in specificity or require reagents.

Purpose of the Study:

• To develop a novel reagentless optical biosensor for glutamine detection.
• To engineer the Escherichia coli glutamine binding protein (GlnBP) for enhanced sensing capabilities.
• To validate the biosensor's specificity and performance using fluorescence-based assays.

Main Methods:

• Site-directed mutagenesis was used to create single cysteine mutants of GlnBP.
• Mutant GlnBP (S179C) was covalently modified with fluorescent probes (acrylodan, IAANS).
• Fluorescence intensity, lifetime, and anisotropy were measured upon glutamine titration.

Main Results:

• GlnBP S179C-acrylodan showed a 65% fluorescence decrease with glutamine (K(Dapp) 160 nM).
• The biosensor demonstrated high specificity, with no significant response to similar amino acids.
• Time-resolved fluorescence and anisotropy measurements confirmed glutamine binding and indicated potential for lifetime-based assays.

Conclusions:

• The engineered GlnBP serves as a sensitive and specific optical biosensor for glutamine.
• This development is a significant step towards nonenzymatic biosensors for cell culture monitoring.
• The reagentless nature of the biosensor offers practical advantages for various applications.