title: Polypeptide modification: an improved proglycinin design to stabilise oil-in-water emulsions.
abstract: β-Conglycinin and glycinin are soybean major seed storage proteins. Previous studies have shown that adding the extension region of β-conglycinin α subunit improves the emulsifying properties of proglycinin and confers more favourable characteristics than fusing the extension region of β-conglycinin α' subunit or the hypervariable regions (A4IV) of glycinin A1aB1b subunit. To evaluate the polypeptide properties, we designed mutants of A1aB1b subunits fused with truncated versions of A4IV (A4IVcut), α (αcut) or α' (α'cut) extension regions lacking the C-terminus 25 or 31 residues (A4IVC25, αC25 or α'C31), and also A4IVcut and α'cut with αC25 residues added (A4IVcut-αC25 and α'cut-αC25). All the modified proteins displayed conformations similar to the wild type. With good solubilities, the emulsion properties of the modified proteins were much better at ionic strength μ = 0.08 than at μ = 0.5. The modified A1aB1bαcut and A1aB1bα'cut showed poorer emulsion properties than those of A1aB1bα and A1aB1bα'. Replacing the hydrophobic A4IVC25 region of A1aB1bA4IV with hydrophilic αC25 created A1aB1bA4IVcut-αC25, which had the best emulsion stability among these proglycinin mutants. We found that addition of αC25 improves the emulsifying properties of two C-terminally truncated proglycinin variants, thereby illustrating its potential general utility. Our investigation showed that in order to improve the emulsifying ability and emulsion stability of a globular protein, the introduced polypeptide should (i) be highly hydrophilic, (ii) consist of multiple hydrophobic-strong hydrophilic regions comprising at least two alpha helixes, (iii) harbour a terminal α-helix at the end of the C-terminus and (iv) have properties similar to those of αC25.
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan Laboratory for Molecular Cell Biology, Medical Research Council, University College London, London WC1E 6BT, UK.
authors.forename: Krisna
authors.initials: K
authors.lastname: Prak
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Naka
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Mary Rose Gecolea
authors.initials: MR
authors.lastname: Tandang-Silvas
authors.affiliation: Laboratory for Molecular Cell Biology, Medical Research Council, University College London, London WC1E 6BT, UK.
authors.forename: Janos
authors.initials: J
authors.lastname: Kriston-Vizi
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan marunobu@kais.kyoto-u.ac.jp.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Maruyama
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Utsumi
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D052179:Antigens, Plant / Q000737:chemistry / Q000235:genetics*; D004655:Emulsions; D005916:Globulins / Q000737:chemistry / Q000235:genetics*; D057927:Hydrophobic and Hydrophilic Interactions; D009154:Mutation; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D055314:Seed Storage Proteins / Q000737:chemistry / Q000235:genetics*; D030262:Soybean Proteins / Q000737:chemistry / Q000235:genetics*; D013025:Glycine max / Q000737:chemistry / Q000235:genetics
chemical_list: D052179:Antigens, Plant; D004655:Emulsions; D005916:Globulins; D010455:Peptides; D021122:Protein Subunits; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C013894:beta-conglycinin protein, Glycine max; C011474:glycinin
keywords: emulsion; glycinin; polypeptide properties; protein engineering; protein interface