Engineered streptavidin monomer and dimer with improved stability and function.

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Engineering

Background:

• Streptavidin's high affinity for biotin makes it a valuable tool, but its tetrameric structure can hinder certain applications.
• Developing streptavidin mutants with simpler structures is challenging due to the difficulty of maintaining biotin-binding function.

Purpose of the Study:

• To design and characterize a stable, monomeric streptavidin mutant that retains biotin-binding capabilities.
• To explore the potential of engineered streptavidin monomers and dimers for novel molecular applications.

Main Methods:

• Rational design of mutations to enhance monomer stability and biotin affinity.
• In vitro and in vivo characterization of engineered streptavidin monomers and dimers.
• Construction and analysis of an A/D dimer from a stabilized monomer.

Main Results:

• Engineered streptavidin monomers exhibited increased stability (Tm from 31 to 47 °C) and improved biotin affinity (Kd from 123 to 38 nM).
• A novel A/D dimer was constructed with a Kd of 17 nM, demonstrating conserved biotin binding.
• The engineered monomer and dimer successfully bound biotinylated targets in vivo, showing selective cell labeling.

Conclusions:

• Stable streptavidin monomers and dimers with retained biotin-binding activity have been successfully engineered.
• These mutants offer potential as novel molecular reagents and tools for studying streptavidin's oligomerization.
• The findings provide insights into the structural determinants of streptavidin's high-affinity biotin binding.