An enhanced approach for engineering thermally stable proteins using yeast display.

Many biotechnology applications require the evolution of enhanced protein stability. Using polymerase chain reaction-based recovery of engineered clones during the screen enrichment phase, we describe a yeast display method capable of yielding engineered proteins having thermal stability that substantially exceeds the viability threshold of the yeast host. To this end, yeast-enhanced green fluorescent protein destabilized by dual-loop insertion was engineered to possess a substantially enhanced resistance to thermal denaturation at 70°C. Stabilized proteins were secreted, purified and found to have three- to six-fold increased resistance to thermal denaturation. The validated method enables yeast display-based screens in previously inaccessible regions of the fitness landscape.

Development of GFP-based biosensors possessing the binding properties of antibodies.

Proteins that can bind specifically to targets that also have an intrinsic property allowing for easy detection could facilitate a multitude of applications. While the widely used green fluorescent protein (GFP) allows for easy detection, attempts to insert multiple binding loops into GFP to impart affinity for a specific target have been met with limited success because of the structural sensitivity of the GFP chromophore. In this study, directed evolution using a surrogate loop approach and yeast surface display yielded a family of GFP scaffolds capable of accommodating 2 proximal, randomized binding loops. The library of potential GFP-based binders or ''GFAbs'' was subsequently mined for GFAbs capable of binding to protein targets. Identified GFAbs bound with nanomolar affinity and required binding contributions from both loops indicating the advantage of a dual loop GFAb platform. Finally, GFAbs were solubly produced and used as fluorescence detection reagents to demonstrate their utility.