组氨酸激酶HK853酸碱调控机制的NMR研究

双组分信号转导系统是细菌应对外界刺激和调控自身生理活动的重要系统。组氨酸激酶是双组分信号转导系统的重要组成部分,大多数组氨酸激酶具有多功能性,不仅能自身磷酸化并能把磷酸基团传递给应激调节蛋白(Response regulator,RR)使之磷酸化,还能催化RR的去磷酸化。研究发现组氨酸激酶HK853的功能受pH值调控,该文利用选择性同位素标记方法,通过NMR技术研究了参与HK853与RR468相互作用的关键氨基酸位点。发现DHp结构域His260侧链的pKa值与HK853的磷酸酶活性有很好的对应关系,HK853与底物形成复合物后其pKa值降低,使His260侧链更易于去质子化,有助于HK853磷酸酶活性的提高。阐明了HK853行使磷酸酶功能时的酸碱调控机制。

Investigation on pH Regulatory Mechanism of HK853 by NMR Spectroscopy

A two-component signal transduction system is the most important signal transduction system for bacteria to cope with external stimuli and self regulate physiological activities.Histidine kinase is an important component of the two-component signal transduction system.Most histidine kinases are multifunctional,they could autophosphorylate and then deliver phosphate groups to the cognate response regulators(RR),and they could also catalyze the dephosphorylation of the response regulator proteins.It is found that the dephosphorylation activity of histidine kinase HK853 is pH dependent.The pH regulation mechanism of HK853 is investigated by using selectively isotopic labeling and NMR spectroscopy.It is revealed that the pKa value of His260 side chain involved in the interaction has a good relationship with the pH dependent phosphatase activity of HK853,which will decrease after HK853 forms a complex with the substrate.The deprotonated imidazole ring plays an important role in the catalytic reaction.This change contributes to the enhancement of HK853 phosphatase activity,ensures the efficiency of acid-base regulation and clarifies the acid-base regulation mechanism of HK853 when performing phosphatase function.