Biophysics projects


Determination of ORAI channel subunit stoichiometry


The relative ratio of the different ORAI Ca2+ channels is highly relevant for cell function. However, their heterometric assembly and their stoichiometry are not known. For example, although experimental approaches pointed towards a dimeric structure at rest and a tetrameric structure upon activation, a crystal structure of truncated Drosophila ORAI1 was hexameric. Thus ORAI channel stoichiometry most likely changes during different functional states (i.e. at rest, during initial- and sustained channel activation). For ORAI2 or ORAI3, no structure is known.

Together with Prof. Barbara Niemeyer, Molecular Biophysics, Saarland University, Homburg, Germany, we explore the stoichiometry of ORAI channels. We use correlative light microscopy and liquid-phase electron microscopy to visualize single ORAI ion channel subunits labeled with fluorescent nanoparticles in intact cells in their liquid state. The cellular location and the stoichiometry of these proteins will thus be studied in the intact plasma membrane, contrasting conventional biochemical approaches based on extracting the proteins from the membrane. See: Alansary et al. 2020

This research is funded by the DFG and is part of the Collaborative Research Centre 1027 entitled “Physical modeling of non-equilibrium processes in biological systems”.