Swanson R V, Bourret R B, Simon M I
Division of Biology, California Institute of Technology, Pasadena 91125.
Mol Microbiol. 1993 May;8(3):435-41. doi: 10.1111/j.1365-2958.1993.tb01588.x.
CheA is a dimeric autophosphorylating protein kinase that plays a critical role in the signal transduction network controlling chemotaxis in Escherichia coli. The autophosphorylation reaction was analysed using mutant proteins defective in kinase and regulatory functions. Proteins in which the site of autophosphorylation was mutated (CheA48HQ) or missing (CheAs) were found to phosphorylate the kinase-defective mutant, CheA470GK. The kinetics of this reaction support the hypothesis that autophosphorylation is the result of trans-phosphorylation within a dimer. The carboxy-terminal portion of CheA was previously shown to be dispensable for autophosphorylation, but required for regulation in response to environmental signals transmitted through a transducer and CheW. Mixing of CheA48HQ or CheA470GK with a truncated protein lacking this regulatory domain demonstrated that regulated autophosphorylation requires the presence of both carboxy-terminal portions in a CheA dimer. These results indicate that the dimeric form of CheA plays an integral role in signal transduction in bacterial chemotaxis.
CheA是一种二聚体自磷酸化蛋白激酶，在控制大肠杆菌趋化性的信号转导网络中起关键作用。利用在激酶和调节功能方面存在缺陷的突变蛋白对自磷酸化反应进行了分析。发现自磷酸化位点发生突变（CheA48HQ）或缺失（CheAs）的蛋白能够磷酸化激酶缺陷型突变体CheA470GK。该反应的动力学支持了自磷酸化是二聚体内反式磷酸化结果的假说。CheA的羧基末端部分先前已被证明对于自磷酸化是可有可无的，但对于响应通过传感器和CheW传递的环境信号进行调节是必需的。将CheA48HQ或CheA470GK与缺乏该调节结构域的截短蛋白混合表明，受调节的自磷酸化需要CheA二聚体中两个羧基末端部分的存在。这些结果表明，CheA的二聚体形式在细菌趋化性的信号转导中起着不可或缺的作用。
