Structure and dynamics of enzymes using site directed spin labeling

Within the projects subsumed here the group works on the development of methodology to characterize the structure and dynamics of enzymes adsorbed to surfaces. There are currently three main direction of research. One of the projects develops within the framework of the Cluster of Excellence UNICAT site directed spin labeling of enzymes – in this particular case sulfite oxidase – containing a large number of native cysteine residues rendering usual cysteine coupling chemistry impossible. We are using the strategy to incorporate non-native amino acids into the protein sequence to allow for specific coupling of spin labels even in the presence of multiple native cysteine residues.

A second project is engaged in the detailed evaluation of the dynamics of the MTSSL spin label using EPR of protein single crystals. Here, we aim at a better description of the spin label dynamics. In particular we will investigate to what extent typically used models to describe the line shape of cw-EPR spectra of spin labeled proteins are valid, which becomes possible for single crystals having only few molecules with well-defined relative orientations in the system.

The third project focuses on the development of systems to study integral membrane proteins on planar surfaces by EPR spectroscopy. Within the project we want to study structural changes of the tethered proteins and to elucidate the possibility to control such changes by changing the properties of the support e.g. an electrostatic potential applied to the surface. The project involves questions of surface chemistry, resonator design, as well as molecular biology to prepare the mutated membrane proteins.