Utrecht University

Biomedical Solid-State NMR

Utrecht University

Shifts in the selectivity filter dynamics cause modal gating in K+ channels 

Sudden active shifts (so called ‘modal gating shifts’) at constant experimental conditions without external stimulus are a common regulatory mechanism in ion channels. Despite the fundamental importance of modal gating behaviour for ion channel function, its molecular origins are very poorly understood.

Together with the group of Benoît Roux, we succeeded to unravel the molecular underpinning of modal gating shifts using an extensive set of 1H-detected solid-state NMR relaxation experiments and MD simulations. Altogether, our study establishes the shifts in the conformational dynamics of the selectivity filter as the key physiological determinant of modal gating shifts in ion channels. At the same time, this work provides a long-needed quantitative description of the selectivity filter dynamics in a native environment, which is of fundamental importance to understand ion channel function. Given that the filter dynamics are strongly different in mutants that mimic voltage-gated potassium channels, this study provides critical clues to better understand eukaryotic potassium channels.

Check out the paper in Nature Communications - Jekhmane & Medeiros-Silva et al.

K+ channels cluster in reference to their gating cycle

Using a combination of dynamic nuclear polarisation (DNP) enhanced solid-state NMR measurements in bacterial membranes and large-scale computer simulations, we could recently show that K+ channels aggregate and dissolve  in reference to their gating cycle, uncovering a hitherto unknown mechanism of functional coupling between K+ channels.

Check out the paper in  Angewandte Chemie 2017 - Visscher et al.

The selectivity filter is subjected to slow dynamics on functional timescales

The selectivity filter of potassium channels is highly conserved throughout bacteria and eukaryotes. Using modern 1H-detected solid-state NMR, we demonstrate that the conductive selectivity  filter exhibits substantially increased slow microsecond motion. Such slow motion is on the same time-scale as thus far unexplained gating modes such as flickering.

Check out the paper in Angewandte Chemie 2016 - Medeiros-Silva et al.  

Buried water in K+ channels

Buried water molecules behind the selectivity filter act as 'gatekeepers', i.e., they are decisive for the conformational state of the inactivation gate/selectivity filter of K+ channels. This was first shown in an elegant computational paper by the group of Benoît Roux (Nature 2013). We have provided the first experimental evidence for the presence of these crucial buried water molecules behind the filter in membranes.

Check out the papers in JACS 2014  and Angewandte Chemie 2015

K+ channel - lipid interaction...

K+ channels are critically modulates by specific lipid interactions, however, such protein-lipid interactions are tricky to probe at high-resolution. By integrating solid-state NMR experiments, MD simulations, and single channel conductance measurements, we could show that anionic lipids critically modulate the activity of the KcsA K+ channel (see here for the paper in JACS 2013 Weingarth et al.).

Furthermore, using NMR and MD simulations, we could demonstrate that anionic lipids are important for the plasticity of K+ channels in reference to the gating mode (see here for the paper in PNAS 2013).