Pflüger Tobias, Hernández Camila F, Lewe Philipp, Frank Fabian, Mertens Haydyn, Svergun Dmitri, Baumstark Manfred W, Lunin Vladimir Y, Jetten Mike S M, Andrade Susana L A
Institute for Biochemistry, University of Freiburg, Albertstr. 21, Freiburg, 79104, Germany.
European Molecular Biology Laboratory, Hamburg Unit, EMBL c/o DESY, Notkestr. 85, Hamburg, D-22603, Germany.
Nat Commun. 2018 Jan 11;9(1):164. doi: 10.1038/s41467-017-02637-3.
Sensing and uptake of external ammonium is essential for anaerobic ammonium-oxidizing (anammox) bacteria, and is typically the domain of the ubiquitous Amt/Rh ammonium transporters. Here, we report on the structure and function of an ammonium sensor/transducer from the anammox bacterium "Candidatus Kuenenia stuttgartiensis" that combines a membrane-integral ammonium transporter domain with a fused histidine kinase. It contains a high-affinity ammonium binding site not present in assimilatory Amt proteins. The levels of phosphorylated histidine in the kinase are coupled to the presence of ammonium, as conformational changes during signal recognition by the Amt module are transduced internally to modulate the kinase activity. The structural analysis of this ammonium sensor by X-ray crystallography and small-angle X-ray-scattering reveals a flexible, bipartite system that recruits a large uptake transporter as a sensory module and modulates its functionality to achieve a mechanistic coupling to a kinase domain in order to trigger downstream signaling events.
感知和摄取外部铵对于厌氧氨氧化（anammox）细菌至关重要，这通常是普遍存在的Amt/Rh铵转运蛋白的功能范畴。在此，我们报道了来自厌氧氨氧化细菌“斯图加特库氏菌（Candidatus Kuenenia stuttgartiensis）”的一种铵传感器/转导器的结构和功能，它将膜整合铵转运结构域与融合的组氨酸激酶相结合。它含有一个在同化性Amt蛋白中不存在的高亲和力铵结合位点。激酶中磷酸化组氨酸的水平与铵的存在相关联，因为在信号被Amt模块识别过程中的构象变化会在内部传导，以调节激酶活性。通过X射线晶体学和小角X射线散射对这种铵传感器进行的结构分析揭示了一个灵活的二分系统，该系统招募一个大型摄取转运蛋白作为传感模块，并调节其功能，以实现与激酶结构域的机制性偶联，从而触发下游信号事件。
