Research

We engineer enzymes whose activity can be controlled by light. Compared with chemical effectors, light offers a decisive advantage: it can be applied with precise spatial and temporal control, and its effect is reversible. This turns enzymes into tools for triggering and dissecting individual steps of a biological process, both in vitro and in living cells.

Our approach rests on the internal insertion of light-sensitive LOV domains into the target enzyme. Upon illumination with blue light, the LOV domain changes its conformation. Placed at a suitable position, it transmits this change to structure and dynamics of the enzyme and thereby switches its activity on or off. The choice of insertion site is critical: it must preserve the fold of the enzyme while coupling the conformational change to catalysis. We recently established this principle for T7 RNA polymerase.

We are currently transferring the insertion approach to protein kinases. Kinases regulate virtually all cellular signalling pathways, and their dysregulation is linked to numerous diseases. Dissecting individual signalling events requires tools that do not permanently inhibit or activate a kinase, but switch its activity in a defined manner.

The tyrosine kinase Abl (Abelson murine leukemia oncogene) serves as our model system. We have identified and biochemically characterised first insertion positions for a LOV domain. Because suitable positions are difficult to predict rationally, we are establishing a selection system in E. coli that allows libraries of insertion variants to be screened in parallel for light-dependent activity. This combines rational protein design with evolutionary methods, an approach that has long characterised our work.