Mechanism of pharmacochaperoning in a mammalian KATP channel revealed by cryo-EM.

ATP-sensitive potassium (KATP) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic ß-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse KATP inhibitors are known to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of a mammalian KATP channel bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. We found all three drugs bind within a common pocket in SUR1. Further, we found the N-terminus of Kir6.2 inserted within the central cavity of the SUR1 ABC core, adjacent the drug binding pocket. The findings reveal a common mechanism by which diverse compounds stabilize the Kir6.2 N-terminus within SUR1's ABC core, allowing it to act as a firm 'handle' for the assembly of metastable mutant SUR1-Kir6.2 complexes.

A new method for ranking potential hazards and risks from wastes.

A quantitative approach for assessing hazards facilitates decision making on hazardous waste management practices. In this study, a scoring approach was developed to evaluate the physical, human health, environmental and amenity hazard aspects and risks (in case of exposure) of waste streams. The approach was based on the 15 hazard properties (HPs) defined in European Commission Waste Framework Directive 2008/98/EC and their related Globally Harmonised System of Classification and Labelling of Chemicals (GHS) hazard statement codes (H-codes). Additionally, amenity and other hazards including space requirement, odour, dust, vermin, visual impact, radioactivity and physical injury were considered. A score of 0-3 was assigned to each of the H-codes or amenity and other hazards. The scoring approach consisted of: 1) determining the waste composition; 2) searching H-codes based on waste composition and assigning H-codes to the associated HPs; 3) calculating the hazard score for each of the four hazard aspects; and 4) calculating the total score for each waste. Two methods were used to calculate the total hazard score for 29 hazardous wastes. The wastes were ranked over a hazard spectrum to indicate the potential degree of hazard. The new hazard scoring approach can be used for prioritising efforts in managing wastes.

Presence of electrolyte promotes wetting and hydrophobic gating in nanopores with residual surface charges.

Hydrophobic nanopores provide a model system to study hydrophobic interactions at the nanoscale. Such nanopores could also function as a valve since they halt the transport of water and all dissolved species. It has recently been found that a hydrophobic pore can become wetted i.e. filled with condensed water or an aqueous solution of salt when a sufficiently high electric field is applied across the membrane. The wetting process is reversible thus when the voltage is lowered or switched off, the pore comes back to a closed state due to water evaporation in the pore. In this manuscript we present experimental studies on how the switching between conducting and non-conducting states can be regulated by the electrolyte concentration. Transport properties of single nanopores modified with alkyl chains of different lengths were recorded in salt concentrations between 10 mM and 1 M KCl. Nanopores modified with propyl chains exhibited gating in 10 mM KCl and were open for ionic transport for all voltages at higher salt concentrations. Nanopores modified with decyl chains did not conduct current in 10 mM and exhibited repeatable hydrophobic gating in 100 mM and 1 M KCl. The results are explained in the context of Maxwell stress in confined geometry with local surface charges, which change the shape of the water-vapor interface and promote wetting.

Velocity profiles in pores with undulating opening diameter and their importance for resistive-pulse experiments.

Pores with undulating opening diameters have emerged as an analytical tool enhancing the speed of resistive-pulse experiments, with a potential to simultaneously characterize size and mechanical properties of translocating objects. In this work, we present a detailed study of the characteristics of resistive-pulses of charged and uncharged polymer particles in pores with different aspect ratios and pore topography. Although no external pressure difference was applied, our experiments and modeling indicated the existence of local pressure drops, which modified axial and radial velocities of the solution. As a consequence of the complex velocity profiles, pores with undulating pore diameter and low-aspect ratio exhibited large dispersion of the translocation times. Distribution of the pulse amplitude, which is a measure of the object size, was not significantly affected by the pore topography. The importance of tuning pore geometry for the application in resistive-sensing and multipronged characterization of physical properties of translocating objects is discussed.