Caspase-6 Undergoes a Distinct Helix-Strand Interconversion upon Substrate Binding.
Caspase-6 Undergoes a Distinct Helix-Strand Interconversion upon Substrate Binding.
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DOI：
10.1074/jbc.m116.773499
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发表时间：
2017-03-24
影响因子：
4.8
通讯作者：
Hardy, Jeanne A.
中科院分区：
文献类型：
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作者：
Dagbay, Kevin B.;Bolik-Coulon, Nicolas;Hardy, Jeanne A.
半胱天冬酶是半胱氨酸天冬氨酸蛋白酶，其是关键细胞过程（包括凋亡和炎症）中的主要参与者。具体而言，半胱天冬酶-6也被认为在神经变性中发挥独特和关键的作用;然而，半胱天冬酶-6与其他半胱天冬酶活性位点之间的结构相似性阻碍了半胱天冬酶-6的精确靶向。所有的半胱天冬酶都可以以典型构象存在，其中底物结合在130'区域中的β链平台的顶部。该半胱天冬酶-6区域也可以采用在任何其他半胱天冬酶中未观察到的螺旋构象。了解caspase-6中螺旋和链构象之间的动力学和相互转换对于充分评估其独特的功能和调节至关重要。在这里，氢/氘交换质谱法表明，caspase-6是固有的和显着更多的构象动态比密切相关的caspase-7。与胱天蛋白酶-7（其在底物结合之前和之后组成性地处于链构象）相反，L2 '和130'区域中的氢/氘交换数据表明，在底物结合之前，胱天蛋白酶-6存在于螺旋和链构象之间的动态平衡中。胱天蛋白酶-6仅在底物结合时才转变为典型的链构象。Glu-135在螺旋和链构象中显示出明显不同的计算pK（a）值，似乎在螺旋和链构象之间的相互转换中发挥关键作用。由于半胱天冬酶-6在几种神经退行性疾病中发挥作用，因此利用本文确定的独特结构特征和构象变化可能为调节特定的半胱天冬酶-6功能以用于治疗目的提供新途径。
Caspases are cysteine aspartate proteases that are major players in key cellular processes, including apoptosis and inflammation. Specifically, caspase-6 has also been implicated in playing a unique and critical role in neurodegeneration; however, structural similarities between caspase-6 and other caspase active sites have hampered precise targeting of caspase-6. All caspases can exist in a canonical conformation, in which the substrate binds atop a beta-strand platform in the 130' s region. This caspase-6 region can also adopt a helical conformation that has not been seen in any other caspases. Understanding the dynamics and interconversion between the helical and strand conformations in caspase-6 is critical to fully assess its unique function and regulation. Here, hydrogen/deuterium exchange mass spec-trometry indicated that caspase-6 is inherently and dramatically more conformationally dynamic than closely related caspase-7. In contrast to caspase-7, which rests constitutively in the strand conformation before and after substrate binding, the hydrogen/deuterium exchange data in the L2 ' and 130' s regions suggested that before substrate binding, caspase-6 exists in a dynamic equilibrium between the helix and strand conformations. Caspase-6 transitions exclusively to the canonical strand conformation only upon substrate binding. Glu-135, which showed noticeably different calculated pK(a) values in the helix and strand conformations, appears to play a key role in the interconversion between the helix and strand conformations. Because caspase-6 has roles in several neurodegenerative diseases, exploiting the unique structural features and conformational changes identified here may provide new avenues for regulating specific caspase-6 functions for therapeutic purposes.