Channel properties of template assembled alamethicin tetramers.
The multiple conductance levels displayed by the antibiotic alamethicin in planar lipid bilayers is explained by a dynamic 'barrel-stave' model, the conducting pore resulting from the aggregation of up to ten helical amphipathic helical monomers. However, the precise assignment of an oligomerization state to a particular single-channel conductance substate is far from being experimentally clear. In addition, it could be useful to tailor a given channel geometry to selectively allow the permeation of solutes with different molecular sizes, whilst retaining a high voltage-dependence. To control the aggregation state of the channel, the TASP (template assembled synthetic proteins) strategy was applied to synthesize structurally defined oligomers, i.e. dimer, trimer, tetramer. The modulation of conductance properties of three alamethicin tetramers with the length and flexibility of the linkers of the 'open' or linear template is described. It is shown that the introduction of an alanine between the contiguous lysines to which are tethered C-terminally modified alamethicin helical monomers stabilizes the open channel states, whereas the alanine substitution by Pro-Gly, a reverse beta-turn promoting motif, increases voltage-dependence and leads to single-channel conductance values more in line with the expected ones from a tetrameric bundle.
Duclohier
Hervé
H
UMR 6026 CNRS-Université de Rennes I, Bâtiment 13, Campus de Beaulieu, 35042 Rennes, France. Herve.Duclohler@univ-rennesl.fr
Alder
Glenn
G
Kociolek
Karol
K
Leplawy
Miroslaw T
MT
D000408:Alamethicin / Q000737:chemistry*; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry; D019281:Dimerization; D004594:Electrophysiology; D005656:Fungal Proteins / Q000737:chemistry*; D007473:Ion Channels / Q000138:chemical synthesis* / Q000502:physiology; D007476:Ionophores / Q000737:chemistry*; D008051:Lipid Bilayers; D018716:Molecular Mimicry
D000900:Anti-Bacterial Agents; D005656:Fungal Proteins; D007473:Ion Channels; D007476:Ionophores; D008051:Lipid Bilayers; D000408:Alamethicin