Institut de Biologie StructuraleGrenoble / France


1. Delineating the relationships between structure, dynamics and function of membrane proteins

Membrane proteins perform a wide range of tasks in the cell, and act as the main interface between a cell and the exterior, and between different cellular compartments. Among the primary tasks of membrane proteins is the transport of molecules through the lipid bilayer. The substrates to be transported range from small metal ions all the way to entire proteins of tens of kilodalton. The mechanisms that underlie these transport processes are as variable as the substrate, but they have a common feature: transport generally relies on conformational changes and dynamics.
Studying molecular dynamics at atomic resolution is a challenging, in particular for membrane proteins, which naturally reside and function in the phospholipid bilayer.

We are using different NMR techniques and different membrane and membrane-mimicking environments to probe functional aspects of membrane proteins. We use solution-state NMR methods, applied to membrane proteins reconstituted in micelles and nanodiscs, as well as solid-state NMR, applied to membrane proteins in a close-to-native lipid bilayer.

Our aim is to understand the relationship of motion and transport. We are focusing on human membrane proteins, and try to understand their mechanisms of action, and the mechanisms by which disease-related mutants dysfunction.

2. Structural biology of molecular chaperones

Chaperones are fascinating machines that assist other proteins in their folding, and prevent them from aggregating. Chaperones are particularly difficult to study by structural methods, because (i) their client proteins are typically disordered and flexible and (ii) chaperones themselves are often hundreds of kilodalton in size. Along this encounter of two challenging fields - disordered, flexible proteins and very large macromolecular architectures - we are using NMR spectroscopy in order to investigate the interactions and motions in these complexes.

4. Studying proteins in interaction with entire cell walls

Solid-state NMR is uniquely suited to study biomolecules in complex environments, such as entire cells or cell walls. In collaboration with the cell-wall team, we are studying the complex of different bacterial proteins interacting with intact bacterial cell walls. In this way, we wish to overcome some of the main limitations of the reductionist structural biology approach, by directly looking at a close-to-native environment.
The understanding of these complexes in terms of structure and dynamics not only represents a fundamental interest, but it might also guide the search for new antibiotic agents, and thus address current global challenges of antibiotic resistance.

5. Solid-state NMR methods for the characterization of biomolecular dynamics and structure

Solid-state NMR spectroscopy has over the past decade made enormous progress, in terms of the kind of systems that can be studied, and the information that one can obtain about (bio-)molecular systems.
The key to these ever-growing capabilities of the technique is the development and improvement of spectroscopic techniques, hardware as well as isotope-labelling approaches.

An important branch of our activity is the development of solid-state NMR methodology. In particular, we are interested in the possibilities of proton-detected solid-state NMR for the study of protein dynamics and structure.

In terms of dynamics studies, we have, for example, developed methods that allow to study at great detail how protein side chains dynamically sample different rotamer positions, or methods that allow to see protein states which are only very transient and low-populated. Such states often turn out to be crucial for biomolecular function.

The study of protein dynamics in the solid-state, and the comparison to the protein motion in solution allows us also to address some fundamental biophysical questions, such as the impact of the environment onto protein flexibility. Along these lines, we are complementing experimental investigations with MD simulations, in order to obtain mechanistic insights.

In terms of structure determination, we are combining advanced isotope labeling techniques, for example with our collaborators, in order to obtain robust structure determination methods based on the measurements of unambiguous, long-range proton-proton distances.