1.C.121 The Soybean Glycinin-derived Pore-forming Peptide (SGPP) Family
Xiang et al. 2016 developed a methodology based on mechanistic evaluation of peptide-lipid bilayer interactions to identify antimicrobial peptides (AMPs) from soy proteins, a methodology that is also applicable for identification of AMPs from other proteins. Initial screening of peptide segments from soy glycinin (11S) and soy beta-conglycinin (7S) subunits, seed storage proteins accumulated during seed development and hydrolyzed after germination to provide a carbon and nitrogen source for the developing seedling, was based on their hydrophobicity, hydrophobic moment and net charge. Balance between hydrophilic and hydrophobic interactions is necessary for pore formation. High hydrophobicity decreases the peptide solubility in aqueous phase whereas high hydrophilicity limits binding of the peptide to the bilayer. Out of several candidates chosen from the initial screening, two peptides satisfied the criteria for antimicrobial activity, viz. (i) lipid-peptide binding in surface state and (ii) pore formation in transmembrane state of the aggregate. Their antimicrobial activity against Listeria monocytogenes and Escherichia coli was demonstrated. The two peptides are: 7a16 (FQTLFKNQYGHVRVLQRFNK) from the β-conglycinin α-chain (P11827) and G5466 (VFKTHHNAVSSYIKDVFRVI) from the glycinin A3 subunit (glycinin B4 subunit). Both peptides are of 20 aas and span themembrane once, forming an oligomeric (tetrameric?) pore (Xiang et al. 2016).