PDF(Pubmed)
Abstract：
The polysialyltransferases ST8SIA2 and ST8SIA4 and their product, polysialic acid (polySia), are known to be related to cancers and mental disorders. ST8SIA2 and ST8SIA4 have conserved amino acid (AA) sequence motifs essential for the synthesis of the polySia structures on the neural cell adhesion molecule. To search for a new motif in the polysialyltransferases, we adopted the in silico Individual Meta Random Forest program that can predict disease-related AA substitutions. The Individual Meta Random Forest program predicted a new eight-amino-acids sequence motif consisting of highly pathogenic AA residues, thus designated as the pathogenic (P) motif. A series of alanine point mutation experiments in the pathogenic motif (P motif) showed that most P motif mutants lost the polysialylation activity without changing the proper enzyme expression levels or localization in the Golgi. In addition, we evaluated the enzyme stability of the P motif mutants using newly established calculations of mutation energy, demonstrating that the subtle change of the conformational energy regulates the activity. In the AlphaFold2 model, we found that the P motif was a buried β-strand underneath the known surface motifs unique to ST8SIA2 and ST8SIA4. Taken together, the P motif is a novel buried β-strand that regulates the full activity of polysialyltransferases from the inside of the molecule.
摘要：
多唾液酸转移酶ST8SIA2和ST8SIA4及其产物，聚唾液酸（polysia），已知与癌症和精神障碍有关。ST8SIA2和ST8SIA4具有对于神经细胞粘附分子上polySia结构的合成所必需的保守氨基酸序列基序。为了在聚唾液酸转移酶中寻找新的基序，我们采用了可以预测疾病相关氨基酸替换的计算机模拟个体Meta随机森林程序(inMeRF)。InMeRF预测了一个新的由高致病性氨基酸残基组成的八氨基酸序列基序，因此指定为致病（P）基序。P基序中的一系列丙氨酸点突变实验表明，大多数P基序突变体失去了聚唾液酸化活性，而没有改变适当的酶表达水平或在高尔基体中的定位。此外,我们使用新建立的突变能量计算评估了P基序突变体的酶稳定性，证明构象能的细微变化调节了活性。在AlphaFold2模型中，我们发现P基序是隐藏在ST8SIA2和ST8SIA4特有的已知表面基序下方的β链。一起来看,P基序是一种新的埋藏的β链,其从分子内部调节聚唾液酸转移酶的全部活性。
