Modification of Solubility and Heat-Induced Gelation of Amaranth 11S Globulin by Protein Engineering

• Published in: Journal of agricultural and food chemistry Vol. 61; no. 14; pp. 3509 - 3516
• Main Authors: Carrazco-Peña, Laura, Osuna-Castro, Juan A, De León-Rodríguez, Antonio, Maruyama, Nobuyuki, Toro-Vazquez, Jorge F, Morales-Rueda, Juan A, Barba de la Rosa, Ana P
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 10-04-2013
• Subjects: Amaranthus - chemistry; Biological and medical sciences; Cereal and baking product industries; Dietary Proteins - chemistry; Dietary Proteins - metabolism; Dietary Supplements; differential scanning calorimetry; Food industries; food industry; Food, Formulated; functional properties; Fundamental and applied biological sciences. Psychology; gelation; Gels; globulins; Globulins - chemistry; Globulins - genetics; Globulins - metabolism; Hot Temperature; hydrophobicity; ionic strength; new products; Phase Transition; Protein Conformation; Protein Engineering; protein structure; recombinant proteins; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Seed Storage Proteins - chemistry; Seed Storage Proteins - genetics; Seed Storage Proteins - metabolism; Seeds - chemistry; Solubility; Surface Properties; recombinant proteins; site directed mutagenesis; Amaranthus hypochondriacus 11S globulins; thermal-mechanical properties; molecular modeling; Protein engineering; Modification; Temperature; Gelation; Site directed mutagenesis; Solubility; Mechanical properties; Environmental factor; Amaranthaceae; Modeling; Globulin; Thermal properties; Heat; Amaranth; Pseudocereals; Dicotyledones; Angiospermae; Amaranthus; Spermatophyta; Recombinant protein
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf3050999

The primary structure of amaranth 11S globulin (Ah11S) was engineered with the aim to improve its functional properties. Four continuous methionines were inserted in variable region V, obtaining the Ah11Sr+4M construction. Changes on protein structure and surface characteristics were analyzed in silico. Solubility and heat-induced gelation of recombinant amaranth 11S proglobulin (Ah11Sr and Ah11Sr+4M) were compared with the native protein (Ah11Sn) purified from amaranth seed flour. The Ah11Sr+4 M showed the highest surface hydrophobicity, but as consequence the solubility was reduced. At low ionic strength (μ = 0.2) and acidic pH (<4.1), the recombinant proteins Ah11Sr and Ah11Sr+4 M had the highest and lowest solubility values, respectively. All globulins samples formed gels at 90 °C and low ionic strength, but Ah11Sn produced the weakest and Ah11Sr the strongest gels. Differential scanning calorimetry analysis under gel forming conditions revealed only exothermic transitions for all amaranth 11S globulins analyzed. In conclusion, the 3D structure analysis has revealed interesting molecular features that could explain the thermal resistance and gel forming ability of amaranth 11S globulins. The incorporation of four continuous methionines in amaranth increased the hydrophobicity, and self-supporting gels formed had intermediate hardness between Ah11Sn and Ah11Sr. These functional properties could be used in the food industry for the development of new products based on amaranth proteins.