The sting. Melittin forms channels in lipid bilayers.

Area of Science:

• Biochemistry
• Biophysics
• Membrane Biology

Background:

• Melittin, a cationic polypeptide from bee venom, interacts with cell membranes.
• Its amphipathic structure, with hydrophobic and polar regions, influences membrane interactions.

Purpose of the Study:

• To investigate the channel-forming properties of melittin in lecithin bilayers.
• To elucidate the voltage-dependence and concentration-dependence of melittin-induced membrane conductance.

Main Methods:

• Electrophysiological measurements of membrane conductance.
• Varying melittin concentration and transmembrane voltage.
• Analysis of conductance changes in response to electrical potential.

Main Results:

• Melittin forms channels in lecithin bilayers, exhibiting anion selectivity.
• Conductance increases with the fourth power of melittin concentration.
• Voltage-dependent conductance is observed, increasing with positive membrane potential.

Conclusions:

• Four melittin monomers likely form a functional channel.
• A minimum of four electronic charges are displaced by the electric field, explaining voltage dependence.