Exploring the interaction of the surfactant N-terminal domain of (gamma)-Zein with soybean phosphatidylcholine liposomes

Zeins are maize storage proteins that accumulate inside large vesicles called protein bodies. (gamma)-Zein lines the inner surface of the protein body membrane, and its N-terminal, proline-rich, repetitive domain with the sequence (VHLPPP)8 appears to be necessary for the accumulation of the protein within the organelle. Synthetic (VHLPPP)8 adopts an amphipathic polyproline II conformation and forms cylindrical micelles in aqueous solution. Here we explore the interaction of (VHLPPP)8 with soybean phosphatidylcholine unilamellar lipid vesicles and examine its effect on the stability and permeability of the liposome membrane. The amphipathic N-terminal domain of (gamma)zein interacts with the membrane and assembles to form extended domains over the phospholipid membrane. The interaction between the peptide and the membrane increases the stability and permeability of the liposome membrane. The spontaneous amphipathic aggregation of (VHLPPP)8 on the membrane suggests a mechanism of (gamma)-zein deposition inside maize protein bodies.