Lu W, Li S, Li G-F, Gong Y-D, Zhao N-M, Zhang R-X, Zhou H-M
Department of Agronomy, Nanjing Agricultural University, Nanjing, 210095, China.
Biochemistry (Mosc). 2002 Aug;67(8):940-4. doi: 10.1023/a:1019978923575.
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a key enzyme in photosynthesis and photorespiration. The inactivation and subsequent conformational changes and dissociation of rice Rubisco by SDS have been studied. At low SDS concentrations (0.4 mM), Rubisco completely lost its carboxylase activity and most of its sulfhydryl groups became exposed. Dissociation of small subunits and significant conformational changes occurred at higher SDS concentrations. Increasing SDS concentrations caused only slight changes in CD spectrum, indicating no significant effect of SDS on the secondary structure of the enzyme. The results prove that the active site of Rubisco is more fragile to denaturants than the protein as a whole. The results also suggest that small subunits are more liable to SDS denaturation and thus dissociate first, while the more hydrophobic large subunits remain complexed. The naturally existing hydrophobic surface of Rubisco may be an important factor in the interaction of Rubisco with other macromolecules.
1,5-二磷酸核酮糖羧化酶/加氧酶（Rubisco）是光合作用和光呼吸中的关键酶。已经研究了SDS对水稻Rubisco的失活以及随后的构象变化和解离。在低SDS浓度（0.4 mM）下，Rubisco完全丧失其羧化酶活性，并且其大部分巯基暴露出来。在较高SDS浓度下，小亚基解离并发生显著的构象变化。增加SDS浓度仅导致圆二色光谱（CD光谱）发生轻微变化，表明SDS对该酶的二级结构没有显著影响。结果证明，Rubisco的活性位点比整个蛋白质对变性剂更敏感。结果还表明，小亚基更容易受到SDS变性作用，因此首先解离，而疏水性更强的大亚基则保持复合状态。Rubisco天然存在的疏水表面可能是Rubisco与其他大分子相互作用的重要因素。
