花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律

Structural Variations in the Subunits of Arachin and Conarachin under Acidic Conditions

本文通过Zeta电位、内源荧光光谱、粒度、SDS-PAGE凝胶电泳及溶解性,探讨花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律。电泳分析表明,花生球蛋白40.5、37.5、35.5和27 ku亚基在常温p H 2.0-3.0的条件下被酸解,产生32.86±0.10ku的新亚基,同时22和15 ku这两条亚基增多;当p H〈2.0时,花生球蛋白的亚基酸解受静电屏蔽抑制。当p H为1.0-3.0,伴花生球蛋白Ⅱ61 ku亚基被酸解产生36.95±0.50、25.14±1.86、18.98±0.78和17.37±1.17 ku这四个条带。进一步研究表明,花生球蛋白和伴花生球蛋白在酸性条件下结构伸展,粒径增大,在p H 2.0-3.0时的Zeta电位及溶解度较高。在p H 2.0-3.0内,花生球蛋白荧光扫描最大发射波长相对中性条件下发生红移,红移幅度大于伴球蛋白,说明伴球蛋白展开程度较球蛋白小。伴花生球蛋白的酸解及结构变化程度都小于球蛋白,说明伴花生球蛋白亚基对酸的敏感性低于球蛋白。

The structural variations in the subunits of arachin and conarachin under acidic conditions were investigated by zeta potential,intrinsic fluorescence spectroscopy,average hydrodynamic diameter analyses,sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE）,and solubility.According to the electrophoretic analysis,the 40.5 ku,37.5 ku,35.5 ku,and 27 ku subunits of arachin were acid-hydrolyzed into a new 32.86 ± 0.10 ku band; while the levels of the 22 ku and 15 ku bands increased.When the p H was 2.0,the acid hydrolysis of arachin was totally inhibited by the electrostatic shielding that occurs at extreme p H.In the p H range of 1.0-3.0,the 61 ku subunit of conarachin was acid-hydrolyzed into 36.95 ± 0.50,25.14 ± 1.86,18.98 ± 0.78,and 17.37±1.17 ku bands.Further studies indicated that both arachin and conarachin unfolded under acidic conditions,and the particle size increased; when the p H values were in the range of 2.0-3.0,the zeta potential and solubility were relatively higher than that in other p H ranges.In the p H 2.0-3.0 range,the maximum emission wavelength in the fluorescence spectra of arachin was red-shifted as compared to that under neutral conditions; and the amplitude of this redshift was greater than that of conarachin,indicating that the degree of conarachin unfolding was lesser than that of arachin.In sum,the degrees of hydrolysis and structural changes of conarachin were lesser than those of arachin,indicating that conarachin is less acid-sensitive than arachin.