Stabilization of enzymes by Proside

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Stable enzymes are of central importance in biotechnology, and the understanding of the principles of protein stability is a major goal in structural biology. Previously we developed an in-vitro selection method for stabilized proteins, termed Proside. It links the resistance towards proteolysis of the protein to be stabilized with the infectivity of a filamentous phage, which is a selectable property. We propose to further optimize the Proside method and then to employ it for the thermodynamic stabilization of enzymes. We will start by using TEM-1 b-lactamase as a model enzyme, and then extend the studies to k-carrageenase, an enzyme that is used in the food industry. In the second part of this project we intend to use Proside to elucidate how modern (ba)8 barrel enzymes might have evolved after the duplication of primordial (ba)4 half barrels. We hope to gain insight into how the interaction surfaces and the energetic cooperativity between domains might nave been formed. To understand the results of these in-vitro selection experiments, many protein variants will be produced, and their functions and stabilities will be elucidated by biophysical techniques. Based on these analyses we will cooperate with the theoreticians of this program to ultimately understand the molecular basis of the observed evolutionary stabilizations.