Mapping temperature-dependent conformational change in the voltage-sensing domain of an engineered heat-activated K ⁺ channel

Abstract

Temperature-dependent regulation of ion channel activity is critical for a variety of physiological processes ranging from immune response to perception of noxious stimuli. Our understanding of the structural mechanisms that underlie temperature sensing remains limited, in part due to the difficulty of combining high-resolution structural analysis with temperature stimulus. Here, we use NMR to compare the temperature-dependent behavior of Shaker potassium channel voltage sensor domain (WT-VSD) to its engineered temperature sensitive (TS-VSD) variant. Further insight into the molecular basis for temperature-dependent behavior is obtained by analyzing the experimental results together with molecular dynamics simulations. Our studies reveal that the overall secondary structure of the engineered TS-VSD is identical to the wild-type channels except for local changes in backbone torsion angles near the site of substitution (V369S and F370S). Remarkably however, these structural differences result in increased hydration of the voltage-sensing arginines and the S4–S5 linker helix in the TS-VSD at higher temperatures, in contrast to the WT-VSD. These findings highlight how subtle differences in the primary structure can result in large-scale changes in solvation and thereby confer increased temperature-dependent activity beyond that predicted by linear summation of solvation energies of individual substituents.

Wireless Neuromodulation at Submillimeter Precision via a Microwave Split-Ring Resonator

“…The rotational spectrum of water lies in the 5 to 125 cm -1 range [37], which overlaps with the frequency range of microwaves. This likely implicates altered behaviors of water molecules at the membrane-water interface [38, 39] and/or crevices in ion channels [40, 41] upon microwave irradiation. In addition, perturbation in interfacial water properties is also expected to affect the solvation of ions, also leading to changes in ion channel activities [42, 43].…”

Efficient Sampling of Cavity Hydration in Proteins with Nonequilibrium Grand Canonical Monte Carlo and Polarizable Force Fields

“…Well-positioned water molecules are often observed in enzyme active sites to stabilize high-energy intermediates or to mediate proton transfers as part of acid–base catalysis. , Low-barrier hydrogen bonding networks consisting of internal water molecules have also been proposed to form the basis of co-operativity between distant catalytic sites in multidomain enzymes . In ion channels and transporters, the transport of metal ions, polar substrates or protons is often facilitated by a network of water molecules embedded in the protein interior. − Changes in the hydration level of protein cavities, pores or crevices have been proposed to be an important component of the gating mechanism for ion transport regulation. − In the context of ligand binding, water molecules in the binding pocket have been shown to contribute significantly to binding affinity and selectivity through either enthalpic or entropic factors. − Therefore, for both mechanistic analysis of protein function and rational ligand design for biomedical applications, determination of the hydration level of protein cavities or binding pockets is of major significance.…”