Institute for Microbiology and Wine Research, Johannes Gutenberg-University, Mainz, Germany.
Microbiologyopen. 2013 Dec;2(6):912-27. doi: 10.1002/mbo3.127. Epub 2013 Sep 9.
The cytoplasmic PASC domain of the fumarate responsive sensor kinase DcuS of Escherichia coli links the transmembrane to the kinase domain. PASC is also required for interaction with the transporter DctA serving as a cosensor of DcuS. Earlier studies suggested that PASC functions as a hinge and transmits the signal to the kinase. Reorganizing the PASC dimer interaction and, independently, removal of DctA, converts DcuS to the constitutive ON state (active without fumarate stimulation). ON mutants were categorized with respect to these two biophysical interactions and the functional state of DcuS: type I-ON mutations grossly reorganize the homodimer, and decrease interaction with DctA. Type IIA-ON mutations create the ON state without grossly reorganizing the homodimer, whereas interaction with DctA is decreased. The type IIB-ON mutations were neither in PASC /PASC , nor in DctA/DcuS interaction affected, similar to fumarate activated wild-typic DcuS. OFF mutations never affected dimer stability. The ON mutations provide novel mechanistic insight: PASC dimerization is essential to silence the kinase. Reorganizing the homodimer and its interaction with DctA activate the kinase. The study suggests a novel ON homo-dimer conformation (type IIB) and an OFF conformation for PASC . Type IIB-ON corresponds to the fumarate induced wild-type conformation, representing an interesting target for structural biology.
大肠杆菌延胡索酸响应传感器激酶 DcuS 的细胞质 PASC 结构域将跨膜结构域与激酶结构域连接起来。PASC 对于与作为 DcuS 共受体的转运蛋白 DctA 的相互作用也是必需的。早期的研究表明，PASC 作为铰链发挥作用，并将信号传递给激酶。重组 PASC 二聚体相互作用，并且独立地去除 DctA，将 DcuS 转化为组成型 ON 状态（无需延胡索酸刺激即可激活）。ON 突变体根据这两种生物物理相互作用和 DcuS 的功能状态进行分类：I 型-ON 突变体严重重组同源二聚体，并降低与 DctA 的相互作用。IIA 型-ON 突变体在不严重重组同源二聚体的情况下产生 ON 状态，而与 DctA 的相互作用降低。IIB 型-ON 突变体既不受 PASC/PASC 影响，也不受 DctA/DcuS 相互作用影响，类似于激活的野生型 DcuS。OFF 突变体从不影响二聚体稳定性。ON 突变体提供了新的机制见解：PASC 二聚化对于沉默激酶是必需的。重组同源二聚体及其与 DctA 的相互作用可激活激酶。该研究提出了一种新型的 ON 同源二聚体构象（IIB 型）和 PASC 的 OFF 构象。IIB 型-ON 对应于延胡索酸诱导的野生型构象，代表了结构生物学的一个有趣目标。
