The interplay between specificity and stability in lactamases: molecular modeling of flexibility and dynamics

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In the proposed project we develop a general molecular model to describe and predict how structure, flexibility, and dynamics of serine lactamases is modified by destabilizing mutations that improve specificity, thus transferring extended spectrum lactamase activity or inhibitor resistance, and mutations that increase stability, but have no effect to activity. Our working hypothesis is that destabilization and stabilization could result from either of two mechanism: from well-known local effects like packing, electrostatics, hydrogen bonding, and solvent effects, or from long-range effects like increased backbone flexibility and coupling of motions, as it has been suggested only recently. We will study these mechanisms by massive multiple molecular dynamics simulations and de novo protein design tools. Understanding the interplay of destabilizing and stabilizing mutations would help to understand natural evolution and provide a design strategy which could be generally used in protein engineering. Predictions of our model are validated by a co-operation with three experimental partners: (1) Detection of new stabilizing mutants by directed evolution and biochemical characterization of engineered mutants (Prof. Dr. Kristian Müller, Freiburg, in the framework of SPP 1170). (2) If promising, an NMR study of protein backbone flexibility will be carried out (Dr. Jörn Werner, University of Southampton) (3) Analysis of lactamase variants isolated from clinical samples (PD Dr. Till Bachmann, Institute of Technical Biochemistry, Stuttgart).