Allostery in ion channels controls activation coupled inactivation and partly controls mean open time. Solid state NMR experiments on full length wild type channel in proteoliposomes provide evidence for evacuation of ions from the selectivity filter during inactivation and strong coupling between opening and ion affinity. Furthermore, a number of site specific mutants altered in their inactivation properties in the hinge of the inner helix (e.g. F103A) suggest that a group of bulky residues serve as “hotspots” for allostery. The plasticity of ion channels is clearly critical to the many essential processes they carry out in all cells. Methods for characterizing millisecond and microsecond conformational exchange processes in high resolution SSNMR experiments will also be discussed.
The talk will also discuss structures of amyloids involved in human biology, and new NMR methods to sensitize detection of signals. RIPK1:RIPK3 core complex of the necrosome, which initiates TNF-induced necroptosis in the context of immune defense, cancer and neurodegenerative diseases. Using solid-state NMR, we determined the high-resolution structure of the core. RIPK1 and RIPK3 assume serpentine conformations, with short β-segments. Packing analogous to other amyloids results in a hydrophobic core with both hetero and homo hydrophobic contacts, and unusual exposed “ladders” of interacting amino acids. The molecularly detailed structure of a hetero-oligomeric amyloid and provides insights into the mechanisms of signal transduction and of inhibition of necroptosis.