Eukaryotic cells are organised in membrane-bound compartments, which have defined chemical identities and carry out specific essential functions. Exchange of material between these compartments is necessary to maintain cell functionality, and is achieved in a highly specific and regulated manner by vesicular transport.
To mediate protein trafficking, coat complexes assemble on membranes and couple bilayer deformation with cargo capture into transport carriers. How coat assembly can deliver the flexibility necessary to accommodate a wide variety of cargo proteins, and how the process can be regulated, are outstanding questions which our lab is aiming to answer.
We are particularly interested in the COPII coat, which mediates export from the ER of about a third of newly synthesized proteins. COPII assembles into two concentric layers and can form transport carriers of a variety of shapes and sizes, including tubules and spherical vesicles. This is important for export of large cargoes and is a process targeted by cargo-specific regulatory factors.
We use a combination of structural and functional approaches to characterise COPII coat assembly, and its role in membrane remodelling. In particular, we use cryo-electron tomography and subtomogram averaging to understand the architecture of the coat layers.
These techniques uniquely target complex structures while achieving high resolutions, ideally suited to obtain a complete view of the COPII coat assembled on membranes.