Stehle Juliane, Fleming Jennifer R, Bauer Piera-Maria, Mayans Olga, Drescher Malte
Department of Chemistry and Konstanz Research School of Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany.
Department of Biology, University of Konstanz, Universitätsstraße 10, 78457, Konstanz, Germany.
Chembiochem. 2023 Oct 4;24(19):e202300408. doi: 10.1002/cbic.202300408. Epub 2023 Aug 11.
The N2A segment of titin functions as a pivotal hub for signal transduction and interacts with various proteins involved in structural support, chaperone activities, and transcriptional regulation. Notably, the "unique N2A" (UN2A) subdomain has been shown to interact with the stress-regulated cardiac ankyrin repeat protein (CARP), which contributes to the regulation of sarcomeric stiffness. Previously, the UN2A domain's three-dimensional structure was modelled based on its secondary structure content identified by NMR spectroscopy, considering the domain in isolation. In this study, we report experimental long-range distance distributions by electron paramagnetic resonance (EPR) spectroscopy between the three helixes within the UN2A domain linked to the immunoglobulin domain I81 in the presence and absence of CARP. The data confirm the central three-helix bundle fold of UN2A and show that this adopts a compact and stable conformation in absence of CARP. After binding to CARP, no significant conformational change was observed, suggesting that the UN2A domain retains its structure upon binding to CARP thereby, mediating the interaction approximately as a rigid-body.
肌联蛋白的N2A片段作为信号转导的关键枢纽，与参与结构支撑、伴侣活性和转录调控的多种蛋白质相互作用。值得注意的是，“独特的N2A”（UN2A）亚结构域已被证明与应激调节的心脏锚蛋白重复蛋白（CARP）相互作用，这有助于调节肌节硬度。此前，UN2A结构域的三维结构是基于通过核磁共振光谱确定的二级结构内容建模的，当时是孤立地考虑该结构域。在本研究中，我们报告了通过电子顺磁共振（EPR）光谱在存在和不存在CARP的情况下，UN2A结构域内与免疫球蛋白结构域I81相连的三个螺旋之间的实验性远程距离分布。数据证实了UN2A的中央三螺旋束折叠，并表明在不存在CARP的情况下，它采用紧凑且稳定的构象。与CARP结合后，未观察到明显的构象变化，这表明UN2A结构域在与CARP结合时保留其结构，从而大致作为刚体介导相互作用。
