Magi 5, from the hexathelid spider Macrothele gigas, is a 29-residue polypeptide containing three disulfide bridges. It binds specifically to receptor site 4 on mammalian voltage-gated sodium channels and competes with scorpion beta-toxins, such as Css IV from Centruroides suffusus suffusus. As a consequence, Magi 5 shifts the activation voltage of the mammalian rNav1.2a channel to more hyperpo...

The well known chloride channel from Torpedo has been a round since 1979 (White and Miller, 1979), but it continues to supply us with new surprises. In this issue of The Journal of General Physiology Chen and Miller analyze in great detail the voltageand chloride-dependent activation mechanism of the peculiar "double-barreled" channel (Chen and Miller, 1996), which turns out to be completely di...

The well known chloride channel from Torpedo has been a round since 1979 (White and Miller, 1979), but it continues to supply us with new surprises. In this issue of The Journal of General Physiology Chen and Miller analyze in great detail the voltageand chloride-dependent activation mechanism of the peculiar "double-barreled" channel (Chen and Miller, 1996), which turns out to be completely di...

Sodium currents mediated by voltage-sensitive sodium channels in normal and scorpion toxin-resistant neuroblastoma cells were measured using a giga-ohm seal recording method in the whole cell patch configuration. The voltage and time dependence of sodium currents were similar in normal and mutant cell lines. Half-maximal activation occurred for test depolarizations in the range of -7 to -11 mV....

The effects of TsIV-5, a toxin isolated from the Brazilian scorpion Tityus serrulatus, on whole-cell and single-channel Na currents were determined in N18 neuroblastoma cells. In whole-cell records at a test potential of -10 mV, external application of 500 nM TsIV-5 slowed inactivation 20-fold and increased peak current by about one-third without changing time-to-peak. Both the steady-state act...

Saxitoxin (STX) selectively blocks the voltage-gated sodium channel at the outer vestibule lined by P-loops of the four domains. Neosaxitoxin has an additional -OH group at the N1 position of the 1,2,3 guanidinium (N1-OH) that interacts with domains I and IV of the Na(+) channel. Determination of a second toxin interaction with the channel would fix the location of STX. Gonyautoxin 2,3 and Gony...

The gating charge and voltage dependence of the open state to the inactivated state (O-->I) transition was measured for the voltage-dependent mammalian cardiac Na channel. Using the site 3 toxin, Anthopleurin-A (Ap-A), which selectively modifies the O-->I transition (see Hanck, D. A., and M. F. Sheets. 1995. Journal of General Physiology. 106:601-616), we studied Na channel gating currents (Ig)...

Vacuolating cytotoxin (VacA) is one of the most important virulence factors of H. pylori (Hp), which isthe only toxic protein that is secreted from Hp cell into the culture supernatant. The effects of VacA oneukaryotic systems is the subject of many previous and on going research studies. Intracellular targetsfor this toxin include: late endosomal and lysosomal compartments, m...

Immunotoxins synthesized with the pan-T-cell monoclonal antibody T101 and ricin, acetylricin, or ricin A-chain have been compared. Native ricin was acetylated with N-acetylimidazole to block the galactose-binding site of the toxin B (binding)-chain. In the presence of lactose, both whole-ricin-containing immunotoxins were selectively cytotoxic but the ricin A-chain conjugate was less effective ...

PURPOSE The human fetal cell line RPE 28 SV4 has been useful for studies of oxidative stress and apoptosis in retinal pigmented epithelium. This cell model is now assessed in functional investigations of chloride channel activity. The study aims to determine the presence of specific chloride channels, including CFTR and ClC channels, to identify the properties of membrane chloride currents and ...