Tamavidin 2-HOT, a highly thermostable biotin-binding protein

Area of Science:

• Biochemistry
• Protein Engineering
• Biotechnology

Background:

• Tamavidin 2 is a fungal tetrameric protein known for high-affinity biotin binding, similar to avidin and streptavidin.
• Existing biotin-binding proteins like avidin and streptavidin have limitations in stability under harsh conditions.

Purpose of the Study:

• To engineer a highly thermostable variant of tamavidin 2 with enhanced biotin-binding capabilities.
• To investigate the structural basis for the increased stability of the engineered protein.

Main Methods:

• Site-directed mutagenesis was used to replace asparagine-115 with cysteine in tamavidin 2, creating tamavidin 2-HOT.
• Biotin-binding activity was assessed after incubation under extreme temperatures (99.9°C) and in organic solvents (70% DMSO).
• Thermal denaturation studies (Tm) and the effect of reducing agents were analyzed to understand the stabilization mechanism.

Main Results:

• Tamavidin 2-HOT retained over 80% of its biotin-binding activity after incubation at 99.9°C for 60 minutes and was fully active in 70% DMSO.
• The melting temperature (Tm) of tamavidin 2-HOT was at least 20°C higher than that of avidin, streptavidin, and wild-type tamavidin 2.
• The enhanced stability was attributed to the formation of disulfide bridges, as evidenced by the loss of stability upon addition of a reducing agent.
• Tamavidin 2-HOT is produced efficiently in soluble form by Escherichia coli and possesses a low isoelectric point (7.4) to minimize non-specific binding.

Conclusions:

• The N115C mutation in tamavidin 2 yields a highly thermostable and robust biotin-binding protein, tamavidin 2-HOT.
• Tamavidin 2-HOT demonstrates superior performance compared to avidin and streptavidin under extreme conditions.
• Its stability, production efficiency, and low isoelectric point make tamavidin 2-HOT a valuable tool for diverse biotechnological applications requiring high biotin-binding affinity under challenging environments.