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Characterization and Crystallography of Recombinant 7S Globulins of Adzuki Bean and Structure-Function Relationships with 7S Globulins of Various Crops

Fukuda, T., Maruyama, N., Salleh, M.R.M., Mikami, B., Utsumi, S.
Journal of agricultural and food chemistry 2008 v.56 no.11 pp. 4145-4153
Vigna angularis var. angularis, beans, food composition, globulins, protein structure, crystallography, recombinant proteins, gene expression, Escherichia coli, complementary DNA, thermal stability, hydrophobicity, solubility, amino acid sequences, hydrogen bonding, chemical bonding, protein conformation, electrostatic interactions, structure-activity relationships
The recombinant proteins Adzuki 7S1, Adzuki 7S2, and Adzuki 7S3 were prepared through the Escherichia coli expression systems of three kinds of adzuki bean cDNAs. The recombinant proteins exhibited intrinsic thermal stabilities, surface hydrophobicities, and solubilities, although the homology of their amino acid sequences ranged from 95-98%. To understand why these individual proteins exhibited different properties, their three-dimensional structures were elucidated. The three proteins were successfully crystallized, and the three-dimensional structures of Adzuki 7S1 and Adzuki 7S3 were determined. The properties and structures of these two proteins were comprehensively compared with those of recombinant 7S globulins (soybean β-conglycinins β and α'c and mungbean 8Sα) reported previously. It was likely that cavity sizes, hydrogen bonds, salt bridges, hydrophobic interactions, and lengths of loops determine the thermal stabilities of 7S globulins, and results indicated that cavity sizes strongly contribute to such stability. Surface hydrophobicity was also found to be determined not only by distributions of hydrophobic residues on the molecular surface. Furthermore, solubility at neutral and weak alkaline pH values at μ = 0.08 was found to be dominantly influenced by the electrostatic surface potentials.