Erdem Karatekin, Ph.D.

SNARE proteins constitute the core of the eukaryotic fusion machinery, yet how SNAREs accomplish fusion and the role of regulatory proteins remain unsettled. Novel in vitro fusion assays which can detect single docking and fusion events have great potential for unraveling mechanistic details, but have been suffering from reproducibility and reliability problems. In addition, almost all past in vitro work used small vesicles (SUVs, diameters ~50 nm) which may be good mimics for the smallest organelles such as synaptic vesicles, but are not likely to be good models for fusion reactions involving large organelles such as yeast vacuoles. For the fusion of large membranes, membrane undulations and large numbers of SNARE proteins may be involved, making the adhesion/fusion process qualitatively different from the case for small vesicles for which undulations are lacking and only a few complexes can drive fusion.

I have been developing novel in vitro fusion assays involving three types of membrane structure: supported bilayers (SBLs) which are "infinitely" large membranes which lack undulations due to their interactions with an underlying substrate, SUVs, and giant unilamellar vesicles (GUVs, diameters ~10-50 microns) which provide freely suspended, large membranes. Various combinations of these three types of membranes reconstituted with SNARE proteins allow us to obtain complementary information and to mimic the vast length and time scales of fusion found in nature.

This work was initiated when I was at the Institut de Biologie Physico-Chimique, CNRS FRE 3146, Paris, France, in collaboration with the group of Michael Seagar at Université de la Mediterranée-Aix Marseille 2 and INSERM U641, Marseilles, France. I am currently on leave from the CNRS to continue the work here. On theoretical aspects, we collaborate with Prof. Ben O'Shaughnessy and Jason Warner at Columbia University.