Hammerschmid Dietmar, Germani Francesca, Drusin Salvador I, Fagnen Charline, Schuster Claudio D, Hoogewijs David, Marti Marcelo A, Venien-Bryan Catherine, Moens Luc, Van Doorslaer Sabine, Sobott Frank, Dewilde Sylvia
Proteinchemistry, Proteomics and Epigenetic Signalling, Department of Biomedical Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
Biomolecular & Analytical Mass Spectrometry, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Comput Struct Biotechnol J. 2021 Mar 26;19:1874-1888. doi: 10.1016/j.csbj.2021.03.031. eCollection 2021.
Globin-coupled sensors (GCS) usually consist of three domains: a sensor/globin, a linker, and a transmitter domain. The globin domain (GD), activated by ligand binding and/or redox change, induces an intramolecular signal transduction resulting in a response of the transmitter domain. Depending on the nature of the transmitter domain, GCSs can have different activities and functions, including adenylate and di-guanylate cyclase, histidine kinase activity, aerotaxis and/or oxygen sensing function. The gram-negative delta-proteobacterium expresses a protein with a GD covalently linked to a four transmembrane domain, classified, by sequence similarity, as GCS (GCS). While its GD is fully characterized, not so its transmembrane domain, which is rarely found in the globin superfamily. In the present work, GCS was characterized spectroscopically and by native ion mobility-mass spectrometry in combination with cryo-electron microscopy. Although lacking high resolution, the oligomeric state and the electron density map were valuable for further rational modeling of the full-length GCS structure. This model demonstrates that GCS forms a transmembrane domain-driven tetramer with minimal contact between the GDs and with the heme groups oriented outward. This organization makes an intramolecular signal transduction less likely. Our results, including the auto-oxidation rate and redox potential, suggest a potential role for GCS as redox sensor or in a membrane-bound e/H transfer. As such, GCS might act as a player in connecting energy production to the oxidation of organic compounds and metal reduction. Database searches indicate that GDs linked to a four or seven helices transmembrane domain occur more frequently than expected.
珠蛋白偶联传感器（GCS）通常由三个结构域组成：一个传感器/珠蛋白结构域、一个连接子结构域和一个信号转导结构域。珠蛋白结构域（GD）通过配体结合和/或氧化还原变化而被激活，引发分子内信号转导，从而导致信号转导结构域产生响应。根据信号转导结构域的性质，GCS可以具有不同的活性和功能，包括腺苷酸环化酶和二鸟苷酸环化酶活性、组氨酸激酶活性、趋氧性和/或氧传感功能。革兰氏阴性δ-变形菌表达一种蛋白质，其GD与一个四跨膜结构域共价连接，根据序列相似性分类为GCS（GCS）。虽然其GD已得到充分表征，但其跨膜结构域却并非如此，该结构域在珠蛋白超家族中很少见。在本研究中，通过光谱学方法以及结合低温电子显微镜的天然离子淌度-质谱对GCS进行了表征。尽管分辨率不高，但寡聚状态和电子密度图对于全长GCS结构的进一步合理建模很有价值。该模型表明，GCS形成了一个由跨膜结构域驱动的四聚体，GD之间的接触最少，且血红素基团向外定向。这种结构使得分子内信号转导的可能性降低。我们的结果，包括自氧化速率和氧化还原电位，表明GCS作为氧化还原传感器或在膜结合的电子/质子转移中可能具有潜在作用。因此，GCS可能在将能量产生与有机化合物氧化和金属还原联系起来的过程中发挥作用。数据库搜索表明，与四螺旋或七螺旋跨膜结构域相连的GD出现的频率比预期的要高。
