Rowland Susan L, Burkholder William F, Cunningham Katherine A, Maciejewski Mark W, Grossman Alan D, King Glenn F
Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030 USA.
Mol Cell. 2004 Mar 12;13(5):689-701. doi: 10.1016/s1097-2765(04)00084-x.
Histidine kinases are used extensively in prokaryotes to monitor and respond to changes in cellular and environmental conditions. In Bacillus subtilis, sporulation-specific gene expression is controlled by a histidine kinase phosphorelay that culminates in phosphorylation of the Spo0A transcription factor. Sda provides a developmental checkpoint by inhibiting this phosphorelay in response to DNA damage and replication defects. We show that Sda acts at the first step in the relay by inhibiting autophosphorylation of the histidine kinase KinA. The structure of Sda, which we determined using NMR, comprises a helical hairpin. A cluster of conserved residues on one face of the hairpin mediates an interaction between Sda and the KinA dimerization/phosphotransfer domain. This interaction stabilizes the KinA dimer, and the two proteins form a stable heterotetramer. The data indicate that Sda forms a molecular barricade that inhibits productive interaction between the catalytic and phosphotransfer domains of KinA.
组氨酸激酶在原核生物中被广泛用于监测和响应细胞及环境条件的变化。在枯草芽孢杆菌中，孢子形成特异性基因表达由一个组氨酸激酶磷酸化信号转导途径控制，该途径最终导致Spo0A转录因子的磷酸化。Sda通过响应DNA损伤和复制缺陷抑制这种磷酸化信号转导途径，从而提供一个发育检查点。我们发现Sda通过抑制组氨酸激酶KinA的自身磷酸化作用于信号转导途径的第一步。我们利用核磁共振确定的Sda结构包含一个螺旋发夹。发夹一侧的一簇保守残基介导了Sda与KinA二聚化/磷酸转移结构域之间的相互作用。这种相互作用稳定了KinA二聚体，并且这两种蛋白质形成了一个稳定的异源四聚体。数据表明Sda形成了一个分子屏障，抑制了KinA催化结构域和磷酸转移结构域之间的有效相互作用。
