Smita Joel, Kendrick B. Turner, Sylvia Daunert

Advancements in biotechnology have allowed for the preparation of designer proteins with a wide spectrum of unprecedented chemical and physical properties. A variety of chemical and genetic methods can be employed to tailor the protein's properties, including its stability and various functions. Herein, we demonstrate the production of semisynthetic glucose recognition proteins (GRPs) prepared by truncating galactose/glucose binding protein (GBP) of E. coli and expanding the genetic code via global incorporation of unnatural amino acids into the structure of GBP and its fragments. The unnatural amino acids 5,5,5-trifluoroleucine (FL) and 5-fluorotryptophan (FW) were chosen for incorporation into the proteins. The resulting semisynthetic GRPs exhibit enhanced thermal stability and increased detection range of glucose without compromising its binding ability. These modifications enabled the utilization of the protein for the detection of glucose within physiological concentrations (mM) and temperatures ranging from hypothermia to hyperthermia. This ability to endow proteins such as GBP with improved stability and properties is critical in designing the next generation of tailor-made biosensing proteins for continuous in vivo glucose monitoring.