Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg-University, Mainz, Germany.
Mol Microbiol. 2020 Feb;113(2):369-380. doi: 10.1111/mmi.14425. Epub 2019 Dec 12.
The NreB-NreC two-component system of Staphylococcus carnosus for O sensing cooperates with the accessory nitrate sensor NreA in the NreA-NreB-NreC system for coordinated sensing and regulation of nitrate respiration by O and nitrate. ApoNreA (NreA in the absence of nitrate) interacts with NreB and inhibits NreB autophosphorylation (and activation). NreB contains the phosphatase motif DxxxQ. The present study shows that NreB on its own was inactive for the dephosphorylation of the phosphorylated response regulator NreC (NreC-P), but co-incubation with NreB and NreA stimulated NreC-P dephosphorylation. Either the presence of instead of apoNreA or mutation of the phosphatase motif (D160 or Q164) of NreB abrogated phosphatase activity of NreB. Phosphatase activity was observed for anoxic (active) NreB as well as oxic NreB, therefore the functional state of NreB is not relevant for phosphatase activity. Thus, NreB is a bifunctional sensor kinase with an integral cryptic phosphatase activity. Activation of phosphatase activity and dephosphorylation of NreC-P requires NreA as a cofactor. Accordingly, NreA and nitrate have major and dual roles in NreA-NreB-NreC regulation by (i) inhibiting NreB phosphorylation and (ii) triggering a kinase/phosphatase switch of NreB when present as apoNreA.
肉葡萄球菌的 NreB-NreC 双组分系统用于 O 感应，与硝酸盐辅助传感器 NreA 在 NreA-NreB-NreC 系统中协同作用，以协调 O 和硝酸盐对硝酸盐呼吸的感应和调节。无硝酸盐时的 apoNreA（NreA）与 NreB 相互作用并抑制 NreB 自身磷酸化（和激活）。NreB 包含磷酸酶基序 DxxxQ。本研究表明，NreB 本身对磷酸化应答调节因子 NreC（NreC-P）的去磷酸化没有活性，但与 NreB 和 NreA 共孵育会刺激 NreC-P 的去磷酸化。NreB 的磷酸酶基序（D160 或 Q164）的突变或存在而不是 apoNreA 会破坏 NreB 的磷酸酶活性。在缺氧（活性）NreB 和需氧 NreB 中都观察到了磷酸酶活性，因此 NreB 的功能状态与磷酸酶活性无关。因此，NreB 是一种具有内在隐匿磷酸酶活性的双功能传感器激酶。磷酸酶活性的激活和 NreC-P 的去磷酸化需要 NreA 作为辅助因子。因此，NreA 和硝酸盐在 NreA-NreB-NreC 调控中具有主要和双重作用，（i）抑制 NreB 的磷酸化，（ii）当以 apoNreA 存在时触发 NreB 的激酶/磷酸酶转换。
