1.C.32 The Amphipathic Peptide Mastoparan (Mastoparan) Family
Mastoparans are 14 (sometimes 13 or 15) amino acyl residue, amphipathic, α-helical peptides present in the venom of hornets, wasps and yellow jackets. They exert numerous biological effects including (1) degranulation of mast cells, (2) G-protein receptor mimicry, (3) phospholipase A2 stimulation, and (4) inhibition of Golgi vesicle transport. They all increase bilayer permeability to hydrophilic solutes by forming short lived pores. Because they are too short to span the membrane as amphipathic α-helices (a configuration they assume when in association with membranes), it is thought that they form bundles of peptides in a so called 'barrel-stove' configuration. Pore formation has been demonstrated electrophysiologically as well as by demonstrating increased permeability to hydrophilic molecules and dyes. They also exhibit cytotoxicity, but certain amino acid substitutions reduce the activity (Irazazabal et al. 2016). Their actual transmembrane architecture is unknown.
Amphipathic peptides can cause biological membranes to leak either by dissolving their lipid content via a detergent-like mechanism or by forming pores on the membrane surface (Yang et al. 2022). These modes of membrane damage have been related to the toxicity of amyloid peptides and to the activities of antimicrobial peptides.
The generalized transport reaction catalyzed by mastoparan pores is:
Small molecules (in) Small molecules (out)