IngentaConnect Structure of the core region of the soybean -conglycinin subunit

Authors: Maruyama, Yukie; Maruyama, Nobuyuki; Mikami, Bunzo; Utsumi, Shigeru

Source: Acta Crystallographica Section D, Volume 60, Number 2, 1 February 2004 , pp. 289-297(9)

Abstract:

The crystal structure of the core region of the α′ subunit (α ) of soybean β-conglycinin has been determined at 2.3 Å resolution. α was superimposed on the known crystal structure of the β-conglycinin β subunit with a small root-mean square deviation of 0.77 Å, which is consistent with the high sequence identity of 75.5% between α and the β subunit. It is known that the thermal stability of the β subunit is higher than that of the α′ subunit and that their thermal stabilities are conferred by highly homologous core regions. Comparisons of the three-dimensional structures and primary sequences between α and the β subunit suggest that five factors account for this difference between subunits as regards the difference in thermal stability: (i) the total cavity volume is larger in α , (ii) the cluster of charged residues at the intermonomer interface is smaller in α and α lacks the intermonomer salt bridge of the β subunit, (iii) the solvent-accessible surface is more hydrophobic in α , (iv) there are fewer proline residues in α and (v) a loop region between helix 3 and strand J′ in α is more flexible owing to the insertion of five additional residues. Although more hydrogen bonds were found in α , this difference should be more than compensated for by the combined contributions of these other factors.

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Structure of the core region of the soybean β-conglycinin α′ subunit