珠蛋白耦合传感器(GCS)通常由三个域组成:传感器/珠蛋白,链接器,和发射机域。珠蛋白域(GD),通过配体结合和/或氧化还原变化激活,诱导分子内信号转导,导致递质结构域的响应。根据发射机域的性质,GCS可以有不同的活动和功能,包括腺苷酸和双鸟苷酸环化酶,组氨酸激酶活性,Aerotaxis和/或氧传感功能。革兰氏阴性δ蛋白杆菌硫还原表达一种具有GD的蛋白质,该GD共价连接到四个跨膜结构域,机密,通过序列相似性,作为GCS(GSGCS)。虽然它的GD是完全特征的,不是它的跨膜结构域,这在globin超家族中很少见。在目前的工作中,GsGCS通过光谱和天然离子迁移质谱结合低温电子显微镜进行表征。虽然缺乏高分辨率,低聚态和电子密度图对于进一步合理建模全长GsGCS结构是有价值的。该模型证明GsGCS形成跨膜结构域驱动的四聚体,在GD之间和与向外取向的血红素基团之间具有最小的接触。这种组织使得分子内信号转导不太可能。我们的结果,包括自动氧化速率和氧化还原电位,提示GsGCS作为氧化还原传感器或在膜结合的e/H转移中的潜在作用。因此,GsGCS可能充当将能源生产与有机化合物的氧化和金属还原联系起来的参与者。数据库搜索表明,与四个或七个螺旋跨膜结构域连接的GD的发生频率比预期的要高。
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 Geobacter sulfurreducens expresses a protein with a GD covalently linked to a four transmembrane domain, classified, by sequence similarity, as GCS (GsGCS). While its GD is fully characterized, not so its transmembrane domain, which is rarely found in the globin superfamily. In the present work, GsGCS 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 GsGCS structure. This model demonstrates that GsGCS 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 GsGCS as redox sensor or in a membrane-bound e-/H+ transfer. As such, GsGCS 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.