Physicochemical properties of native and recombinant mungbean (Vigna radiata L. Wilczek) 8S globulins and the effects of the N-linked Glycans

We have previously cloned and characterized the cDNAs of three isoforms of the 8S globulin of mungbean, expressed the major 8S alpha isoform in Escherichia coli, and purified and successfully crystallized it ( Bernardo, A. E. N.; Garcia, R. N.; Adachi, M.; Angeles, J. G. C.; Kaga, A; Ishimoto, M.; Utsumi, S.; Tecson-Mendoza, E. M. J. Agric. Food Chem. 2004, 52, 2552-2560). Herein, we report the physicochemical and emulsifying properties of the native 8S and recombinant 8S alpha globulin or vicilin. The circular dichroism spectra analysis of the native 8S and recombinant 8S alpha globulins revealed that the recombinant 8S alpha formed a secondary structure close to that of the native 8S. Further, gel filtration analysis showed that 8S alpha was able to assemble into trimers. The native 8S and recombinant 8S alpha globulins were soluble at pH 3.4 and at pH 7.4-9.0 at low ionic strength, mu = 0.08. Interestingly, the native 8S was more soluble at pH 7.0 and pH 7.4 than the recombinant 8SR at A) 0.08. Both forms were very soluble at pH 3.4-9.0 at high ionic strength, mu = 0.50. The native form exhibited a higher T-m ( 69.2, 79.5, and 83.8 degrees C) than the recombinant form ( 65.6, 71.6, 77.5 degrees C) at mu = 0.1, 0.2, and 0.5, respectively. The recombinant form was found to have greater surface hydrophobicity than the native form. There was little difference in the emulsifying ability between the native 8S and 8S alpha at pH 3.4 and pH 7.6. The results indicate that the presence of N-linked glycans is not essential in the assembly and stable conformation of the mungbean vicilin. However, the N-linked glycans might have contributed to the higher solubility at low ionic strength, greater thermal stability, and decreased surface hydrophobicity of the native vicilin as compared to the recombinant 8SR. On the other hand, the N-linked glycans showed little effect on the emulsifying ability of the protein.