Protein tyrosine phosphatase PTPN13, also known as PTP-BL in mice, is a large multi-domain non-transmembrane scaffolding protein with a molecular mass of 270 kDa. It is involved in the regulation of several cellular processes such as cytokinesis and actin-cytoskeletal rearrangement. The modular structure of PTPN13 consists of an N-terminal KIND domain, a FERM domain, and five PDZ domains, followed by a C-terminal protein tyrosine phosphatase domain. PDZ domains are among the most abundant protein modules and they play a crucial role in signal transduction of protein networks. Here, we have analysed the binding characteristics of the isolated PDZ domains 2 and 3 from PTPN13 and compared them to the tandem domain PDZ2/3, which interacts with 12 C-terminal residues of the tumour suppressor protein of APC, using heteronuclear multidimensional NMR spectroscopy. Furthermore, we could show for the first time that PRK2 is a weak binding partner of PDZ2 and we demonstrate that the presence of PDZ3 alters the binding affinity of PDZ2 for APC, suggesting an allosteric effect and thereby modulating the binding characteristics of PDZ2. A HADDOCK-based molecular model of the PDZ2/3 tandem domain from PTPN13 supports these results. Our study of tandem PDZ2/3 in complex with APC suggests that the interaction of PDZ3 with PDZ2 induces an allosteric modulation within PDZ2 emanating from the back of the domain to the ligand binding site. Thus, the modified binding preference of PDZ2 for APC could be explained by an allosteric effect and provides further evidence for the pivotal function of PDZ2 in the PDZ123 domain triplet within PTPN13.

中文翻译：

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PTPN13的串联PDZ2 / 3域的结合亲和力是变构调节

蛋白质酪氨酸磷酸酶PTPN13，在小鼠中也称为PTP-BL，是一种大型多域非跨膜支架蛋白，分子量为270 kDa。它参与几种细胞过程的调控，例如胞质分裂和肌动蛋白-细胞骨架重排。PTPN13的模块结构由一个N端KIND域，一个FERM域和五个PDZ域组成，然后是一个C端蛋白酪氨酸磷酸酶结构域。PDZ域是最丰富的蛋白质模块之一，它们在蛋白质网络的信号转导中起着至关重要的作用。在这里，我们分析了从PTPN13分离出的PDZ结构域2和3的结合特性，并将它们与串联结构域PDZ2 / 3（与APC肿瘤抑制蛋白的12个C末端残基相互作用）进行了比较，使用异核多维NMR光谱。此外，我们可以首次证明PRK2是PDZ2的弱结合伴侣，并且我们证明PDZ3的存在改变了PDZ2对APC的结合亲和力，暗示了变构作用，从而调节了PDZ2的结合特性。来自PTPN13的PDZ2 / 3串联结构域的基于HADDOCK的分子模型支持这些结果。我们对与APC复合的串联PDZ2 / 3的研究表明，PDZ3与PDZ2的相互作用诱导了PDZ2中的变构调节，该变构调节是从结构域的背面向配体结合位点发出的。因此，变构效应可以解释PDZ2对APC的结合偏好，并为PTPN13中PDZ123结构域三联体中PDZ2的关键功能提供了进一步的证据。我们可以首次证明PRK2是PDZ2的弱结合伴侣，并且我们证明PDZ3的存在改变了PDZ2对APC的结合亲和力，暗示了变构作用，从而调节了PDZ2的结合特性。来自PTPN13的PDZ2 / 3串联结构域的基于HADDOCK的分子模型支持这些结果。我们对与APC复合的串联PDZ2 / 3的研究表明，PDZ3与PDZ2的相互作用诱导了PDZ2中的变构调节，该变构调节是从结构域的背面向配体结合位点发出的。因此，变构效应可以解释PDZ2对APC的结合偏好，并为PTPN13中PDZ123结构域三联体中PDZ2的关键功能提供了进一步的证据。我们可以首次证明PRK2是PDZ2的弱结合伴侣，并且我们证明PDZ3的存在改变了PDZ2对APC的结合亲和力，暗示了变构作用，从而调节了PDZ2的结合特性。来自PTPN13的PDZ2 / 3串联结构域的基于HADDOCK的分子模型支持这些结果。我们对与APC复合的串联PDZ2 / 3的研究表明，PDZ3与PDZ2的相互作用诱导了PDZ2中的变构调节，该变构调节是从结构域的背面向配体结合位点发出的。因此，变构效应可以解释PDZ2对APC的结合偏好，并为PTPN13中PDZ123结构域三联体中PDZ2的关键功能提供了进一步的证据。