Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Campus UAM, Cantoblanco, 28049 Madrid, Spain.
Environ Microbiol Rep. 2013 Apr;5(2):291-300. doi: 10.1111/1758-2229.12017. Epub 2012 Dec 6.
Sensor kinases play a key role in sensing and responding to environmental and physiological signals in bacteria. In this study we characterized a previously unknown orphan hybrid sensor kinase from Pseudomonas putida, which is conserved in several Pseudomonads. Inactivation of the gene coding for this sensor kinase, which we have named HskA, modified the expression of at least 85 genes in cells growing in a complete medium. HskA showed a strong influence on the composition of the electron transport chain. In cells growing exponentially in a complete medium, the absence of HskA led to a significant reduction in the expression of the genes coding for the bc1 complex and for the CIO and Cbb3-1 terminal oxidases. In stationary phase cells, however, lack of HskA caused a higher expression of the Cyo terminal oxidase and a lower expression of the Aa3 terminal oxidase. The HskA polypeptide shows two PAS (signal-sensing) domains, a transmitter domain containing the invariant phosphorylatable histidine and an ATP binding site, and a receiver domain containing the conserved aspartate capable of transphosphorylation, but lacks an Hpt module. It is therefore a hybrid sensor kinase. Phosphorylation assays showed that purified HskA undergoes autophosphorylation in the presence of ATP.
传感器激酶在细菌中对环境和生理信号的感应和响应中起着关键作用。在这项研究中，我们对一种来自假单胞菌的先前未知的孤儿混合传感器激酶进行了表征，该激酶在几种假单胞菌中保守。失活编码这种传感器激酶的基因，我们将其命名为 HskA，会改变在完全培养基中生长的细胞中至少 85 个基因的表达。HskA 对电子传递链的组成有很强的影响。在完全培养基中指数生长的细胞中，缺乏 HskA 会导致编码 bc1 复合物和 CIO 和 Cbb3-1 末端氧化酶的基因表达显著减少。然而，在静止期细胞中，缺乏 HskA 会导致 Cyo 末端氧化酶的表达增加，Aa3 末端氧化酶的表达降低。HskA 多肽有两个 PAS（信号感应）结构域，一个包含不变的可磷酸化组氨酸的传输结构域和一个 ATP 结合位点，以及一个包含保守的可进行转磷酸化的天冬氨酸的接收结构域，但缺乏 Hpt 模块。因此，它是一种混合传感器激酶。磷酸化实验表明，在 ATP 存在的情况下，纯化的 HskA 会发生自身磷酸化。
