To better understand the molecular events underlying vesicular fusion we explore the physicochemical properties of the protein-protein interactions involved. We want to identify the domains involved, locate the binding surfaces and study the affinities, stoichiometries and kinetics of the interactions and their interplay with membranes to disentangle the entire network. For our biochemical studies, we almost exclusively use recombinant proteins. Next to standard biochemical techniques, we employ spectroscopic (circular dichroism and fluorescence spectroscopy) and calorimetric methods. Where feasible we use high-resolution structural techniques.
RESEARCH & TECHNOLOGY
Concomitantly we want to shed light on the evolutionary history of the vesicle fusion machine, which arose from an ancient prototypic mechanism during the rise of the last eukaryotic common ancestor (LECA) from its prokaryotic-like ancestor. We would like to uncover how the mechanism adapted in different eukaryotic lineages and how it was most probably organized in the proto-eukaryotic cell. A particular focus lies on the evolutionary changes of the repertoire of the secretory machine during the rise of animals. Taking advantage of the huge number of available sequence data sets, our group developed a database to store and analyze sequences of the protein families involved in vesicle trafficking. Sequences are analyzed through iterative use of hidden Markov models and tree building
Morphological & functional investigations
In conjunction, we plan to scrutinize in vivo, the interaction steps that we identified biochemically in vitro. Ultimately we want to correlate the configuration of the (neuro) secretory machinery in the cell with mutations/diseases-related to transport deficiencies. In addition, we are taking a closer look at the very early stages in the evolution of the secretory apparatus by studying the choanoflagellate Monosiga brevicollis and the placozoan Trichoplax adhaerens. Choanoflagellates are a group of mostly single-celled eukaryotes thought to be the closest known sister group to animals; Trichoplax is an animal positioned near the root of the animal tree. It is a simple, free-living marine animal without a nervous system and that glides using cilia to feed on algae. For this, we use, among others, state-of-the-art light and electron microscopy approaches.