Temperature modulates binding specificity and affinity of the D-trehalose/D-maltose-binding protein from the hyperthermophilic archaeon Thermococcus litoralis.

We investigated the effect of temperature on the binding specificity of the recombinant D-trehalose/D-maltose-binding protein from the hyperthermophilic archaeon Thermococcus litoralis (TMBP). Importantly, we found that TMBP can bind D-glucose (Glc). The Glc binding was characterized by means of fluorescence spectroscopy in the temperature range of 25 °C–85 °C. Our results show that at 25 °C the binding of Glc to TMBP is well represented by a bimodal model with apparent Kd of 20 ìM and approximately 3–8 mM for the first and the second binding step, respectively. At 60 °C the binding of Glc to TMBP is represented by a simple hyperbolic model with an apparent Kd value of about 40 ìM. Finally, at 85 °C Glc did not bind to TMBP. Molecular dynamics (MD) simulations were used to shed light on the molecular mechanism of the Glc binding. Our results suggest that after proper fluorescent labeling TMBP can be used as a highly thermostable and non-consuming analyte biosensor for monitoring the level of glucose in fluids (e.g. human blood) where other sugars are not present.