Ion channels formed by a highly charged peptide.
A peptide (MA-beta) corresponding to a segment of the nicotinic acetylcholine receptor (AChR) that has amphipathic alpha-helical periodicity forms ion channels in artificial phospholipid bilayers. The MA-beta ion channels are very stable, comprise two discrete conductance states, and undergo rapid, flickering-type closings. The discrete-conductance ion channels formed by MA-beta contrast with the continuous-conductance ion channels formed by a peptide (M2-delta) identical in sequence with M2 [Oiki, S., Danho, W., Madison, V., & Montal, M. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 8703-8707], a putative transmembrane segment of the AChR. Neither MA-beta nor M2-delta sufficiently mimics the electrophysiological properties of the native AChR. We suggest that peptide ion channels can be classified into at least three general groups: discrete-conductance channels, such as MA-beta; continuous-conductance channels, such as M2-delta; and membrane disruptors, such as those formed by short, amphipathic alpha-helical peptides.
Ghosh
P
P
Department of Biochemistry and Biophysics, University of California, San Francisco 94143.
Stroud
R M
RM
D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism*; D014101:Torpedo
D007473:Ion Channels; D008051:Lipid Bilayers; D010743:Phospholipids; D011950:Receptors, Cholinergic