Ion-channel properties of mastoparan, a 14-residue peptide from wasp venom, and of MP3, a 12-residue analogue.
Mastoparan, a 14-residue peptide, has been investigated with respect to its ability to form ion channels in planar lipid bilayers. In the presence of 0.3-3.0 microM mastoparan, two types of activity are seen. Type I activity is characterized by discrete channel openings, exhibiting multiple conductance levels in the range 15-700 pS. Type II activity is characterized by transient increases in bilayer conductance, up to a maximum of about 650 pS. Both type I and type II activities are voltage dependent. Channel activation occurs if the compartment containing mastoparan is held at a positive potential; channel inactivation if the same compartment is held at a negative potential. Channel formation is dependent on ionic strength; channel openings are only observed at KCl concentrations of 0.3 M or above. Furthermore, raising the concentration of KCl to 3.0 M stabilizes the open form of the channel. Mastoparan channels are weakly cation selective, PK/Cl approximately 2. A 12-residue analogue, des-Ile1,Asn2-mastoparan, preferentially forms type I channels. The ion channels formed by these short peptides may be modelled in terms of bundles of transmembrane alpha-helices.
Mellor
I R
IR
Department of Zoology, University of Nottingham, University Park, U.K.
Sansom
M S
MS
D000595:Amino Acid Sequence; D001514:Bee Venoms; D004553:Electric Conductivity; D036341:Intercellular Signaling Peptides and Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D008564:Membrane Potentials; D008954:Models, Biological; D008961:Models, Structural; D008969:Molecular Sequence Data; D010455:Peptides; D011487:Protein Conformation; D014862:Wasp Venoms
D001514:Bee Venoms; D036341:Intercellular Signaling Peptides and Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan