Redox-dependent conformational changes of a proximal [4Fe-4S] cluster in Hyb-type [NiFe]-hydrogenase to protect the active site from O.

Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe-4S] cluster proximal to the Ni-Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe-4S] to display redox-dependent conformational changes.

Analysis of Ion Transport through a Single Channel of Gramicidin A in Bilayer Lipid Membranes.

Ion transport through a single channel of gramicidin A (GA) within the bilayer lipid membrane (BLM) between two aqueous phases (W1 and W2) has been analyzed based on the electroneutrality principle. The single-channel current increases in proportion to the magnitude of the applied membrane potential and is also dependent on the permeability coefficients of electrolyte ions (K(+) and Cl(-)). By varying the ratio of the concentration of KCl in W1 to that in W2, the ratio of the diffusion coefficient of K(+) in the BLM to that of Cl(-) in the BLM can be evaluated.

Effect of counter ions on the transport current across membranes containing KAT1 potassium channel.

Ion transports from one aqueous phase (W1) to another (W2) across bilayer lipid membranes (BLM) containing KAT1 potassium channel were investigated by recording current fluctuations. KAT1 channel is a voltage-gated K(+) channel from Arabidopsis thaliana and has been suggested to have a key role in stomatal opening by osmoregulation in guard cells. Although KAT1 channel is a K(+)-specific transporter, the species of the counter anions significantly affected the level of the single channel current, suggesting that KAT1 also transported these anions.

Selectivity on ion transport across bilayer lipid membranes in the presence of gramicidin A.

Ion transport from one aqueous (W1) to another (W2) across bilayer lipid membranes (BLM) containing gramicidin A (GA) was investigated by recording current fluctuations, when various alkali metal chlorides and potassium salts were used as supporting electrolytes. The magnitude of the single-channel current at a given membrane potential depended on not only the cationic species, but also on the anionic species, and then it decreased with an increase in the diameter of the anion when the diameter of the anion was larger than the pore size of the GA channel. The baseline of the recording current, however, increased with an increase in the diameter of the anion, and its height depended on the concentration of GA in the BLM.