Responsable : Irina Gutsche

Our group is interested in imaging macromolecular complexes and cells with the goal of gaining structural insights that would yield functional understanding of cellular processes.

Our favorite imaging technique is cryo-electron microscopy: we are using state-of-the art equipment available at the IBS EM platform and further afield to obtain images of our objects of interest. Once we have our images, we combine the most recent image analysis tools to solve the 3D structures of biomolecules. In recent years, we have solved structures of several challenging proteins and complexes, some of which were purified and biologically investigated in our lab, and others provided by collaborators.

While we continue investigating the structure-function relationships of several biological systems with «traditional» single particle cryo-EM, we are critically aware that the bottleneck of all in vitro structural techniques is sample preparation: the object of interest can for instance fall apart during purification, lose its cellular partners or a ligand, miss an essential posttranslational modification and change its oligomeric state. Therefore, we are now developing methods to solve structures directly from cryo-EM images of heterogeneous samples. Altogether, this methodology should enable investigation of the cellular structural proteome in its native state. This project is currently driven by Ambroise Desfosses and Eymeline Pageot.

The method of choice to address the 3D structure of biomolecules in their cellular context is undoubtedly cryo-electron tomography. We took our first steps into the world of cryo-ET with both in vitro reconstituted systems and bacterial minicells, and recently Irina Gutsche and Lorène Gonnin have also embarked on the cryo-FIB-milling and in situ cryo-ET journey. In parallel, we quickly realised that in addition to experimental difficulties, the major problem that newcomers into the cryo-ET field have to face is that optimal processing workflows in cryo-ET and subtomogram averaging are relatively complex and often require combination of diverse software packages. Thus, two PhD students in the group, Alister Burt and Lorenzo Gaifas, create and share their cryo-ET automation, analysis and visualisation tools with the growing cryo-ET community. They also established and maintain a collaborative online resource for sharing knowledge and tools related to cryo-electron tomography data processing.

In addition to cryo-EM, we also use a variety of complementary methods from phenotypic analysis, through biochemistry, biophysics and X-ray crystallography, to advanced optical imaging. From a biological standpoint, the group’s research is mainly centered on microbial stress response, signalling and sensory adaptation, as well as on non segmented negative strand RNA viruses. We are lucky to work with an extensive network of local, national and international collaborators.