Reconstitution of vacuolar ion channels into planar lipid bilayers

A laser microsurgical method of cell wall removal allows detection of large-conductance ion channels in the guard cell plasma membrane

Application of patch clamp techniques to higher-plant cells has been subject to the limitation that the requisite contact of the patch electrode with the cell membrane necessitates prior enzymatic removal of the plant cell wall. Because the wall is an integral component of plant cells, and because cell-wall-degrading enzymes can disrupt membrane properties, such enzymatic treatments may alter ion channel behavior. We compared ion channel activity in enzymatically isolated protoplasts of Vicia faba guard cells with that found in membranes exposed by a laser microsurgical technique in which only a tiny portion of the cell wall is removed while the rest of the cell remains intact within its tissue environment. "Laser-assisted" patch clamping reveals a new category of high-conductance (130 to 361 pS) ion channels not previously reported in patch clamp studies on plant plasma membranes. These data indicate that ion channels are present in plant membranes that are not detected by conventional patch clamp techniques involving the production of individual plant protoplasts isolated from their tissue environment by enzymatic digestion of the cell wall. Given the large conductances of the channels revealed by laser-assisted patch clamping, we hypothesize that these channels play a significant role in the regulation of ion content and electrical signalling in guard cells.

Effects of ADP, DTT, and Mg2+ on the ion-conductive property of chloroplast H+-ATPase(CF0-CF1) reconstituted into bilayer membrane

The purified CF0-CF1 complex of spinach was incorporated into planar lipid bilayer membranes (LBMs) formed with soybean phospholipid, and the transmembrane ion-transmission properties were studied under voltage-clamp mode. The results showed that the presence of both ADP and Pi decreased the membrane current while Dithiothreitol could evoke a stronger conductive change of CF0-CF1 containing LBMs when Ca2+ or Mg2+ exists. Mg2+ can dramatically increase the CF0-CF1 conductance in various conditions. These results indicated that the H(+)-transitive function of CF0-CF1 reconstituted in bilayer is sensitive to those factors which can affect its ATP synthase activity in vivo.

Interaction of phospholipids with proteins and peptides. New advances III

1. The review deals with the recent achievements in the study of the various interactions of phospholipids with proteins and peptides. 2. The interactions are classified according to the hydrophobic, hydrophilic or mixed character of the interactive forces. 3. The effect of the interaction on the structure and biological activity of the interacting molecules is also discussed.