Institut de Pharmacologie et de Biologie Structurale (IPBS) Toulouse,
Department of Structural Biology and Biophysics
Title: NMR Analyses of the Structure and Dynamics of Klebsiella Pneumoniae OmpA Transmembrane Domain
Wednesday, October 18
The transmembrane domain of kpOmpA possesses four long extracellular loops which exhibit substantial sequence vari¬ability throughout OmpA homologues in Enterobacteria. These loops are responsible for the immunological properties of the protein, such as cellular and humoral recognitions. Using liquid state NMR we have determined the 3D structure of kpOmpA in DHPC micelles (M. Renault et al., J. Mol. Biol. 2009). In a micellar environment, a complex dynamical behav¬ior has been observed: a rigid barrel core, ms motion at the micellar-water interface, and sub-ns motions within the loops. Using 1H and 13C detected solid state NMR relaxation measurements and proteolysis experiments, we have demonstrated the persistence of this complex motional behavior in E. coli polar lipid bilayers (I. Iordanov et al., Biochim. Biophys. Acta, 2012; O. Saurel et al., J Amer. chem. Soc., 2017). Using single molecule force spectroscopy we have shown that kpOmpA is able to unfold and refold reversibly its β-barrel core (P. Bosshart et al., Structure 2012). Finally, relaxation violated coher¬ence transfer NMR spectroscopy on Alanine residues provided an accurate determination of order parameters in the loops and barrel residues. These results provide a unique description of internal motion within a membrane protein and allow illustrating the power of liquid and solid state NMR.
The Scientific Community is Invited