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Magni C, Sessa F, Capraro J, Duranti M, Maffioli E, Scarafoni A. Structural and functional insights into the basic globulin 7S of soybean seeds by using trypsin as a molecular probe. Biochem Biophys Res Commun 2018; 496:89-94. [PMID: 29305261 DOI: 10.1016/j.bbrc.2018.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 01/01/2018] [Indexed: 10/18/2022]
Abstract
The basic 7S globulin (Bg7S) is one of the major globulins of soybean seeds. Despite its dual subunit composition and oligomeric assembly, Bg7S has a compact 3D structure (PDB: 3AUP) which is stabilized by a network of inter- and intra-chain disulphide bridges. Bg7S shares several structural elements with a number of homologous proteins from other seeds, whose function is still uncertain. In this work, Bg7S native conformation was probed by using the proteolytic enzyme trypsin. In spite of the presence of many arginine and lysine residues, the protein resulted extremely recalcitrant to in vitro enzymatic cleavage. Indeed, only two scissile bonds located near the C- and N-termini of the large and small subunits, respectively, were cleaved. The partially cleaved products were stable even at prolonged incubation times. Although the generated small peptide fragments were not covalently bound to the remnant of the main chains, they were held in place, as assessed by denaturing and non-denaturing chromatographic approaches. Moreover, both the already observed pH-dependent association/dissociation behaviour of the protein and its insulin binding capacity were preserved both at neutral and acidic pH values. These results are in line with the growing view that the degradation of seed proteins, either storage and non-storage, may be a controlled process related to specific functionalities.
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Affiliation(s)
- Chiara Magni
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Via G. Celoria, 2, 20133, Milan, Italy
| | - Fabio Sessa
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Via G. Celoria, 2, 20133, Milan, Italy
| | - Jessica Capraro
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Via G. Celoria, 2, 20133, Milan, Italy.
| | - Marcello Duranti
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Via G. Celoria, 2, 20133, Milan, Italy
| | - Elisa Maffioli
- Department of Veterinary Medicine (DIMEVET), Università degli Studi di Milano, Via G. Celoria, 10, 20133, Milan, Italy
| | - Alessio Scarafoni
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Via G. Celoria, 2, 20133, Milan, Italy
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