Department of Microbial Pathogenesis and Howard Hughes Medical Institute, Yale School of Medicine, New Haven, CT 06536.
Proc Natl Acad Sci U S A. 2013 Jan 8;110(2):E161-9. doi: 10.1073/pnas.1212102110. Epub 2012 Dec 19.
Cellular processes require specific interactions between cognate protein partners and concomitant discrimination against noncognate partners. Signal transduction by classical two-component regulatory systems typically entails an intermolecular phosphoryl transfer between a sensor kinase (SK) and a cognate response regulator (RR). Interactions between noncognate partners are rare because SK/RR pairs coevolve unique interfaces that dictate phosphotransfer specificity. Here we report that the in vitro phosphotransfer specificity is relaxed in hybrid two-component systems (HTCSs) from the human gut symbiont Bacteroides thetaiotaomicron, which harbor both the SK and RR in a single polypeptide. In contrast, phosphotransfer specificity is retained in classical two-component regulatory systems from this organism. This relaxed specificity enabled us to rewire a HTCS successfully to transduce signals between noncognate SK/RR pairs. Despite the relaxed specificity between SK and RRs, HTCSs remained insulated from cross-talk with noncognate proteins in vivo. Our data suggest that the high local concentration of the SK and RR present in the same polypeptide maintains specificity while relaxing the constraints on coevolving unique contact interfaces.
细胞过程需要同源蛋白伴侣之间的特定相互作用，并同时区分非同源伴侣。经典的双组分调节系统的信号转导通常涉及传感器激酶 (SK) 和同源应答调节蛋白 (RR) 之间的分子间磷酸转移。非同源伴侣之间的相互作用很少见，因为 SK/RR 对共同进化出独特的界面，决定磷酸转移特异性。在这里，我们报告了来自人类肠道共生菌拟杆菌的混合双组分系统 (HTCS) 中体外磷酸转移特异性的放宽，该系统在单个多肽中同时包含 SK 和 RR。相比之下，该生物体的经典双组分调节系统保留了磷酸转移特异性。这种放宽的特异性使我们能够成功地重新布线 HTCS，在非同源 SK/RR 对之间传递信号。尽管 SK 和 RRs 之间的特异性放宽，但 HTCS 在体内仍然与非同源蛋白隔离开来，避免了串扰。我们的数据表明，同一多肽中存在的 SK 和 RR 的高局部浓度在放宽共同进化独特接触界面的约束的同时保持特异性。
