Oxford Centre for Integrative Systems Biology, University of Oxford, Oxford, UK.
Mol Microbiol. 2010 Apr;76(2):318-30. doi: 10.1111/j.1365-2958.2010.07095.x.
Specificity of protein-protein interactions plays a vital role in signal transduction. The chemosensory pathway of Rhodobacter sphaeroides comprises multiple homologues of chemotaxis proteins characterized in organisms such as Escherichia coli. Three CheA homologues are essential for chemotaxis in R. sphaeroides under laboratory conditions. These CheAs are differentially localized to two chemosensory clusters, one at the cell pole and one in the cytoplasm. The polar CheA, CheA(2), has the same domain structure as E. coli CheA and can phosphorylate all R. sphaeroides chemotaxis response regulators. CheA(3) and CheA(4) independently localize to the cytoplasmic cluster; each protein has a subset of the CheA domains, with CheA(3) phosphorylating CheA(4) together making a functional CheA protein. Interestingly, CheA(3)-P can only phosphorylate two response regulators, CheY(6) and CheB(2). R. sphaeroides CheAs exhibit two interesting differences in specificity: (i) the response regulators that they phosphorylate and (ii) the chemosensory cluster to which they localize. Using a domain-swapping approach we investigated the role of the P1 and P5 CheA domains in determining these specificities. We show that the P1 domain is sufficient to determine which response regulators will be phosphorylated in vitro while the P5 domain is sufficient to localize the CheAs to a specific chemosensory cluster.
蛋白质-蛋白质相互作用的特异性在信号转导中起着至关重要的作用。红杆菌的化学感觉途径包含多个趋化蛋白同源物，这些同源物在大肠杆菌等生物中都有特征。在实验室条件下，三种 CheA 同源物对红杆菌的趋化作用是必不可少的。这些 CheAs 分别定位于两个化学感觉簇，一个位于细胞极，另一个位于细胞质中。极地 CheA（CheA(2)）与大肠杆菌 CheA 具有相同的结构域结构，能够磷酸化所有红杆菌趋化反应调节剂。CheA(3)和 CheA(4)独立地定位于细胞质簇；每种蛋白质都有 CheA 结构域的一个子集，CheA(3)与 CheA(4)一起磷酸化，形成功能性 CheA 蛋白。有趣的是，CheA(3)-P 只能磷酸化两个反应调节剂，CheY(6)和 CheB(2)。红杆菌 CheAs 在特异性方面表现出两个有趣的差异：（i）它们磷酸化的反应调节剂和（ii）它们定位于的化学感觉簇。我们使用结构域交换方法研究了 P1 和 P5 CheA 结构域在决定这些特异性中的作用。我们表明，P1 结构域足以决定体外哪些反应调节剂将被磷酸化，而 P5 结构域足以将 CheAs 定位到特定的化学感觉簇。
