TU Braunschweig, Institute of Plant Biology, Braunschweig, Germany.
Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
Protein Sci. 2023 Sep;32(9):e4753. doi: 10.1002/pro.4753.
Within the cell, the trace element molybdenum (Mo) is only biologically active when complexed either within the nitrogenase-specific FeMo cofactor or within the molybdenum cofactor (Moco). Moco consists of an organic part, called molybdopterin (MPT) and an inorganic part, that is, the Mo-center. The enzyme which catalyzes the Mo-center formation is the molybdenum insertase (Mo-insertase). Mo-insertases consist of two functional domains called G- and E-domain. The G-domain catalyzes the formation of adenylated MPT (MPT-AMP), which is the substrate for the E-domain, that catalyzes the actual molybdate insertion reaction. Though the functions of E- and G-domain have been elucidated to great structural and mechanistic detail, their combined function is poorly characterized. In this work, we describe a structural model of the eukaryotic Mo-insertase Cnx1 complex that was generated based on cross-linking mass spectrometry combined with computational modeling. We revealed Cnx1 to form an asymmetric hexameric complex which allows the E- and G-domain active sites to align in a catalytic productive orientation toward each other.
在细胞内，微量元素钼（Mo）只有与氮酶特异性的 FeMo 辅因子或钼辅因子（Moco）结合时才具有生物活性。Moco 由有机部分（称为钼喋呤（MPT））和无机部分，即 Mo 中心组成。催化 Mo 中心形成的酶是钼插入酶（Mo-insertase）。Mo-insertases 由两个功能域组成，称为 G-和 E-域。G-域催化腺苷酸化的 MPT（MPT-AMP）的形成，它是 E-域的底物，催化实际的钼酸盐插入反应。尽管 E-和 G-域的功能已被阐明到非常详细的结构和机制细节，但它们的联合功能还没有得到很好的描述。在这项工作中，我们描述了基于交联质谱结合计算建模生成的真核 Mo-insertase Cnx1 复合物的结构模型。我们揭示了 Cnx1 形成一个不对称的六聚体复合物，允许 E-和 G-域的活性位点彼此对齐，形成催化生产性取向。
