Protein structure, dynamics and function

I use nuclear magnetic resonance (NMR) spectroscopy to study protein structure and dynamics and their relationship with protein function.  Examples of proteins I am interested in include kinases that are involved in cancer or parasitic infection and calmodulin that is a mediator of calcium signaling.  I am also interested in methodology, especially novel NMR experiments and isotopic labeling schemes.

Proteins

Proteins are essential to sustain all forms of life and each protein has a highly specialized function. The common explanation to why proteins can have such specific functions is that each protein has a unique structure and that this structure dictates its physical properties as well as which other molecules it can interact with. This is however a simplified picture. Proteins are dynamic and their structures fluctuate on a wide range of time scales and a complete understanding thus not only requires knowledge of static structures but also of which parts can move, how fast and how much and not the least when they do.

Four proteins of interest to my lab. Clockwise from top left: the kinase domain of EphB2, a PDZ domain from SAP97, calmodulin and TPMT.

NMR spectroscopy

Nuclear magnetic resonance, NMR, spectroscopy is uniquely suited to answer all these questions. NMR spectroscopy takes advantage of the fact that many atomic nuclei behave as tiny magnets that, just like ordinary magnets, can interact with external magnetic fields and with each other. Since it is possible to transfer magnetization between different nuclei in a distance dependent manner, it is possible to measure interatomic distances and thus to determine protein structures and because the shape of the NMR signal depends on motions it is possible to characterize these as well.

Our 600 MHz (left) and 500 MHz (right) NMR spectrometers.

A particularly powerful application of NMR spectroscopy, Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion, allows a very detailed characterization of protein dynamics on the biologically relevant millisecond time-scale in which all rate constants, the populations of all exchanging states as well as the chemical shifts of all excited states even if their low population precludes their direct observation in the NMR spectra. This is very interesting since the chemical shifts in principle encodes the structure.

Projects

        I am studying a class of kinases where protein dynamics are crucial for function. Since kinases are important for signalling and also implicated in various forms of cancers, this is interesting from a medical point of view. Another project aims at characterizing the conformational reorginization of calmodulin upon calcium binding in as much detail as possible.

        I am also involved in development of new methodology, especially new or improved relaxation dispersion experiments and selective isotopic labeling schemes.