Equilibrium unfolding of a 69-kDa monomeric Escherichia coli maltodextrin glucosidase (MalZ) was studied using intrinsic and extrinsic fluorescence spectroscopy. The unfolding transition of MalZ followed a three-state process, involving the formation of a stable intermediate state having more exposed hydrophobic surface. It was found that the protein structure can be easily perturbed by low concentration of guanidium hydrochloride (GdnHCl) and, at a GdnHCl concentration of 2 M, MalZ was denatured completely. The active site of the protein also has been proved to be sensitive to a low concentration of GdnHCl since MalZ deactivated at 0.5 M GdnHCl completely. The surface hydrophobicity and ANS-binding site of the protein have been determined to be 150.7 and 0.24, respectively. Perhaps the formation of the stable unfolding intermediate, having higher surface hydrophobicity, may be one of the reasons for aggregation of MalZ and its recognition by chaperonin GroEL during the assisted folding pathway.

中文翻译：

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通过荧光光谱法监测大肠杆菌麦芽糊精葡萄糖苷酶的展开研究

使用内在和外在荧光光谱研究了 69 kDa 单体大肠杆菌麦芽糖糊精葡萄糖苷酶 (MalZ) 的平衡展开。MalZ 的解折叠转变遵循三态过程，包括形成具有更多暴露疏水表面的稳定中间态。发现低浓度的盐酸胍 (GdnHCl) 很容易扰乱蛋白质结构，并且在 2 M 的 GdnHCl 浓度下，MalZ 完全变性。由于 MalZ 在 0.5 M GdnHCl 下完全失活，因此蛋白质的活性位点也已被证明对低浓度的 GdnHCl 敏感。已确定蛋白质的表面疏水性和 ANS 结合位点分别为 150.7 和 0.24。也许形成稳定的展开中间体，