Structure and Stability of Integral Membrane Protein and Phage Assemblies Team (Cécile Breyton)
Team Leader: Cécile BREYTON (DR CNRS)
Biochemistry of membrane proteins; Biophysics; Crystallography; Small angle X-ray and neutron scattering; Cryoelectron microscopy.
Main Research themes
The structural investigation of the first step of phage infection in the phage T5 – E. coli system.
Phage T5, a virus that infects E. coli, belongs to the family of long, flexible tailed phages. We are interested in understanding the molecular mechanisms of cell wall perforation, which is triggered by the interaction of the tip of the phage tail with its receptor, an E. coli outer membrane protein, FhuA.
In the last years, we have located the eleven proteins of the tail, then embarked in determining the structure of individual tail proteins. The phage proteins being difficult to phase, this work benefited greatly from the phasing agents developed by E. Girard (IBS). We studied T5 tail tube, by cryoelectron microscopy (cryo-EM), before and after interaction with FhuA in collaboration with G. Schoehn (IBS). Combining cryo-EM of the tail tube (6 Å resolution) and the crystal structure of the major tail protein (2.2 Å resolution), we proposed a pseudo-atomic structure of the tail tube. In an ongoing collaboration with P. Schanda (IBS), we are comparing the dynamics of this protein in solution and in it is polymerized form by solution and solid state NMR.
Our project is actually to investigate the structure of T5 tail tip and the channel it forms when interacting with a membrane. We will also investigate the “immunity” of phage T5, by studying the interaction and the structure of Llp, a small phage-encoded periplasmic protein that binds FhuA, preventing over-infection by other phages.
In this context, the team is a member of the Phages.fr thematic network.
The development of methods for the functional and structural studies of membrane proteins.
We are evaluating the physical-chemical and biochemical properties of new detergents and new fluorinated surfactants, designed to be few aggressive toward membrane proteins, in collaboration with G. Durand (Avignon), and S. Keller (Kaiserslautern, DE).
We are evaluating protocols, for the characterization of membrane proteins, using Analytical Ultracentrifugation and Size Exclusion Chromatography coupled to Light Scattering.
Small Angle Neutron Scattering (SANS) is a powerful technique to investigate the solution structure of membrane proteins, in that it allows cancelling the contribution of free micelles and bound detergent. We have used SANS to reveal fast collisional lipid exchange within patches of lipid bilayers stabilised by SMA, an amphipatic polymer used to manipulate membrane proteins. We are studying the conformations of the proteins SpNox and BmrA, in collaboration with F. Fieschi (M&P, IBS), and J.-M. Jault (IBCP, Lyon), respectively, and with A. Martel (ILL).
Structure-function relationships of receptors, channels and transporters; Biophysics and biochemistry; Molecular and structural virology; Bacteriophages; Surfactants.