N-terminal insertion of alamethicin in channel formation studied using its covalent dimer N-terminally linked by disulfide bond.
Alamethicin is supposed to form helix-bundle-type channels by inserting the N terminus into bilayer lipid membranes under sufficient voltages. The N-terminal insertion has been studied with an alamethicin dimer (di-alm) N-terminally linked by a disulfide bond and by the asymmetric addition of dithiothreitol (DTT) and tetrathionate (TT) to the membrane. When di-alm was added to the cis-side membrane, it forms long-lasting channels with the lifetime tau of about 100 ms at cis-positive voltages. The lifetime was reduced to a few milliseconds by addition of DTT to the cis-side membrane, indicating that most of the channels were formed by the monomers (alm-SH) that resulted from the cleavage of the disulfide bond in di-alm. The succeeding addition of TT to the trans-side produced channels of tau=10-20 ms besides the channels of alm-SH. The results suggested that TT reacted with the N-terminal thiol group of alm-SH located at the trans-side of the membrane to alter the lifetime. The N-terminal insertion of alamethicin helices by voltage activation, therefore, was confirmed.
Sakoh
Machiko
M
Institute for Chemical Research, Kyoto University, Uji, 611-0011, Kyoto, Japan.
Okazaki
Takashi
T
Nagaoka
Yasuo
Y
Asami
Koji
K
D000408:Alamethicin / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry*; D004229:Dithiothreitol / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D007473:Ion Channels / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D013776:Tetrathionic Acid / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D004220:Disulfides; D007473:Ion Channels; D008051:Lipid Bilayers; D000408:Alamethicin; D013776:Tetrathionic Acid; D004229:Dithiothreitol