We are investigating the structure, assembly and regulation of plant vacuolar transporters. Among these are two proton pumps: the plant vacuolar pyrophosphatase (V-PPase) and the plant vacuolar ATPase (V-ATPase). The V-ATPase is a multimeric complex of more than 20 proteins encoded by 28 genes in Arabidopsis. Thus, its assembly and quality control are challenging for the plant cell and we are interested in the sequence of subunit interactions and compartmentation of assembly. Furthermore, isoenzymes of the V-ATPase can be found along the secretory pathway, so that assembly has to take place in an isoenzyme-specific manner.

Another subject area is the improvement of in vivo analysis of protein-protein interactions by fluorescence-based approaches like bimolecular fluorescence complementation (BiFC) and Förster resonance energy transfer (FRET). Here, we are interested in multistep FRET-cascades between fluorescent proteins. This aims at the detection of multimeric complex arrangements and at the expansion of FRET as spectroscopic ruler. Currently, we analyse energy transfer cascades between four spectrally distinct fluorescent proteins.

Last but not least we have established a eukaryotic expression system for the analysis of human transcription factors.The system allows for the functional analysis of human signalling pathways in the absence of endogenous factors that potentially interfere with the pathway.


Excitation and Emission spectra of ECFP, EYFP and mCherry. A: spectral overlaps of CFP emission spectrum and emission spectra of EYFP and mCherry. B: Experimental setup for 2-step FRET measurements