Remodeling hydrogen bond interactions results in relaxed specificity of Caspase-3.
Remodeling hydrogen bond interactions results in relaxed specificity of Caspase-3.
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DOI：
10.1042/bsr20203495
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发表时间：
2021-01-29
影响因子：
4
通讯作者：
Clark AC
中科院分区：
文献类型：
--
作者：
Yao L;Swartz P;Hamilton PT;Clark AC
Caspase（或半胱氨酰天冬氨酸特异性蛋白酶）在细胞凋亡和炎症中发挥重要作用，不同但重叠的特异性谱（即切割识别序列）将细胞引导至不同的命运。尽管所有 caspase 均偏好底物 P1 位点的天冬氨酸，但 caspase-6 亚家族偏好 P4 位点的缬氨酸，而 caspase-3 则偏好天冬氨酸。与人类 caspase 相比，来自斑马鱼的 caspase-3a 具有宽松的特异性，并且在 P4 位点对缬氨酸或天冬氨酸具有相同的选择。在 caspase-3 构象景观的背景下，我们发现 S3 亚位点附近氢键的变化会影响 P4 氨基酸的选择。与 caspase-6 交换特异性需要进入新的构象空间，其中每种景观都会导致 DxxD (caspase-3) 或 VxxD (caspase-6) 底物的最佳结合，同时不利于其他底物的结合。在 caspase-3 构象景观中，活性位点附近的取代通过破坏底物结合袋中的氢键网络，导致针对 DxxD 和 VxxD 的活性几乎相同。斑马鱼 caspase-3a 中的相反取代导致 P4 天冬氨酸的选择增加而不是缬氨酸。总体而言，数据表明，与进入新构象空间以交换底物特异性（例如在 caspase-3 和 -6 之间）所需的氨基酸取代相比，导致双功能蛋白酶（如斑马鱼 caspase-3a）的特异性转变需要更少的氨基酸取代。
Caspase (or cysteinyl-aspartate specific proteases) enzymes play important roles in apoptosis and inflammation, and the non-identical but overlapping specificity profiles (that is, cleavage recognition sequence) direct cells to different fates. Although all caspases prefer aspartate at the P1 position of the substrate, the caspase-6 subfamily shows preference for valine at the P4 position, while caspase-3 shows preference for aspartate. In comparison with human caspases, caspase-3a from zebrafish has relaxed specificity and demonstrates equal selection for either valine or aspartate at the P4 position. In the context of the caspase-3 conformational landscape, we show that changes in hydrogen bonding near the S3 subsite affect selection of the P4 amino acid. Swapping specificity with caspase-6 requires accessing new conformational space, where each landscape results in optimal binding of DxxD (caspase-3) or VxxD (caspase-6) substrate and simultaneously disfavors binding of the other substrate. Within the context of the caspase-3 conformational landscape, substitutions near the active site result in nearly equal activity against DxxD and VxxD by disrupting a hydrogen bonding network in the substrate binding pocket. The converse substitutions in zebrafish caspase-3a result in increased selection for P4 aspartate over valine. Overall, the data show that the shift in specificity that results in a dual function protease, as in zebrafish caspase-3a, requires fewer amino acid substitutions compared with those required to access new conformational space for swapping substrate specificity, such as between caspases-3 and -6.