Dhungel Sajina, Xiao Michael, Pushpabai Rajesh Rajaian, Kikani Chintan K
Department of Biology, University of Kentucky, Lexington, KY 40502.
Proc Natl Acad Sci U S A. 2025 Mar 25;122(12):e2409685122. doi: 10.1073/pnas.2409685122. Epub 2025 Mar 19.
PAS domains are ubiquitous sensory modules that transduce environmental signals into cellular responses through tandem PAS folds and PAS-associated C-terminal (PAC) motifs. While this conserved architecture underpins their regulatory roles, here we uncover a structural divergence in the metazoan PAS domain-regulated kinase (PASK). By integrating evolutionary-scale domain mapping with deep learning-based structural models, we identified two PAS domains in PASK, namely PAS-B and PAS-C, in addition to the previously known PAS-A domain. Unlike canonical PAS domains, the PAS fold and PAC motif in the PAS-C domain are spatially segregated by an unstructured linker, yet a functional PAS module is assembled through intramolecular interactions. We demonstrate that this assembly is nutrient responsive and serves to remodel the quaternary structure of PASK that positions the PAS-A domain near the kinase activation loop. This nutrient-sensitive spatial arrangement stabilizes the activation loop, enabling catalytic activation of PASK. These findings revealed an alternative mode of regulatory control in PAS sensory proteins, where the structural assembly of PAS domains links environmental sensing to enzymatic activity. By demonstrating that PAS domains integrate signals through dynamic structural rearrangements, this study broadens the understanding of their functional and regulatory roles and highlights potential opportunities for targeting PAS domain-mediated pathways in therapeutic applications.
PAS结构域是普遍存在的传感模块，通过串联的PAS折叠和与PAS相关的C端（PAC）基序将环境信号转化为细胞反应。虽然这种保守的结构支撑着它们的调节作用，但在此我们发现后生动物PAS结构域调节激酶（PASK）存在结构差异。通过将进化尺度的结构域图谱与基于深度学习的结构模型相结合，我们在PASK中除了先前已知的PAS - A结构域外，还鉴定出另外两个PAS结构域，即PAS - B和PAS - C。与典型的PAS结构域不同，PAS - C结构域中的PAS折叠和PAC基序在空间上被一个无结构的连接子隔开，但一个功能性的PAS模块通过分子内相互作用组装而成。我们证明这种组装对营养物质有反应，并用于重塑PASK的四级结构，使PAS - A结构域定位在激酶激活环附近。这种对营养物质敏感的空间排列稳定了激活环，从而实现PASK的催化激活。这些发现揭示了PAS传感蛋白中一种替代的调节控制模式，即PAS结构域的结构组装将环境感知与酶活性联系起来。通过证明PAS结构域通过动态结构重排整合信号，本研究拓宽了对其功能和调节作用的理解，并突出了在治疗应用中靶向PAS结构域介导途径的潜在机会。
