The 28-111 disulfide bond constrains the alpha-lactalbumin molten globule and weakens its cooperativity of folding.
The 28-111 disulfide bond constrains the alpha-lactalbumin molten globule and weakens its cooperativity of folding.
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28-111二硫键限制了α-乳清蛋白熔球，削弱了其折叠协同性。
DOI：
10.1073/pnas.96.20.11283
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发表时间：
1999
影响因子：
11.1
通讯作者：
Baldwin,RL
中科院分区：
文献类型：
--
作者：
Luo,Y;Baldwin,RL
我们的目的是确定α-乳白蛋白的二硫键是否解释了一些熔融球变体缺乏合作折叠行为的原因，而pH 4的脱辅基肌红蛋白熔融球报道了高度合作折叠。研究了两种不同的α-乳白蛋白遗传构建体：[28-111]，其具有连接α-螺旋结构域的两个片段的单个二硫键，和[全-Ala]，其没有二硫键。先前用于探测脱辅基肌红蛋白熔融球的协同折叠的叠加测试用于确定[28-111]和[all-Ala]的熔融球之间的折叠协同性是否存在重要差异。[全-Ala]结构的行为以相同的方式作为脱辅基肌红蛋白熔融球：其折叠满足叠加测试在三组阴离子条件下研究，和阴离子稳定它对尿素展开。[28-111]结构在这两个方面表现不同：其熔融球的折叠在三组阴离子条件中的两组中不满足叠加检验，阴离子几乎不影响其稳定性。28-111二硫键使熔融球基本上稳定，正如早期工作所预期的那样。通过圆二色性监测的去折叠过渡曲线的比较也表明，[28-111]以比[all-Ala]更不合作的方式折叠：[28-111]的去折叠曲线显著更宽。此外，解折叠曲线表明[28-111]具有比[all-Ala]更低的螺旋含量。因此，28-111键限制了熔融球的折叠行为，削弱了其折叠的协同性。
Our aim is to determine whether the disulfide bonds of α-lactalbumin account for the lack of cooperative folding behavior reported for some molten globule variants, in contrast to the highly cooperative folding reported for the pH 4 molten globule of apomyoglobin. Two different α-lactalbumin genetic constructs are studied: [28–111], which has a single disulfide bond connecting two segments of the α-helix domain, and [all-Ala], which has no disulfide bonds. The superposition test used earlier to probe for cooperative folding of the apomyoglobin molten globule is used to determine whether there is an important difference in folding cooperativity between the molten globules of [28–111] and [all-Ala]. The [all-Ala] construct behaves in the same manner as the apomyoglobin molten globule: its folding satisfies the superposition test in the three sets of anion conditions studied, and anions stabilize it against urea unfolding. The [28–111] construct behaves differently in both respects: the folding of its molten globule does not satisfy the superposition test in two of the three sets of anion conditions, and anions barely affect its stability. The 28–111 disulfide bond stabilizes the molten globule substantially, as expected from earlier work. Comparison of the unfolding transition curves monitored by circular dichroism also demonstrates that [28–111] folds in a less cooperative manner than [all-Ala]: the unfolding curve of [28–111] is significantly broader. Moreover, the unfolding curves indicate that [28–111] has a lower helix content than [all-Ala]. Consequently, the 28–111 bond constrains the folding behavior of the molten globule and weakens its cooperativity of folding.