Thiol/Disulfide Redox Regulation of Heme Oxygenase-2

说明(申请人提供)：血红素加氧酶(HO)催化血红素转化为胆绿素、一氧化碳和铁。HO1和HO2这两种异构体具有相似的物理和动力学性质，但具有不同的生理作用和器官位置。HO1和HO2的核心催化结构域的结构几乎是可重叠的，这些HO亚型之间的主要区别是HO2中存在HO1缺乏的血红素调节基序(HRMS)。HRMS起着硫醇/二硫化物氧化还原开关的调节作用，我们已经证明，它可以调节HO2与底物(血红素)以及钙激活的高电导钾通道(BK或Slopoke通道)的相互作用。通过BK通道调节膜上的钾离子流量，可以使颈动脉小体的氧气感知功能发挥作用，从而控制呼吸系统的通气量，以应对血氧浓度的变化。我们最近证明，BK通道还包含一个硫醇/二硫化物氧化还原开关，该开关调节血红素的结合，这已被证明控制其K通道的活性。我们计划使用光谱、动力学、遗传学、结晶学、核磁共振和电生理学的方法来确定这些硫醇/二硫键氧化还原开关(人类HO2中的HRMS和人类BK通道中的CXXC基序)如何影响这些功能连接的蛋白质的结构和功能以及它们之间的相互作用。我们将在体外和体内测定不同生理条件下血红素和HRMS的氧化还原状态。我们还将进行光谱和电生理测量，以确定HO2影响BK通道功能的机制。

DESCRIPTION (provided by applicant): Heme oxygenase (HO) catalyzes the conversion of heme to biliverdin, CO, and iron. The two isoforms, HO1 and HO2, share similar physical and kinetic properties but exhibit different physiological roles and organ locations. The structures of the core catalytic domains of HO1 and HO2 are nearly superimposable and the major distinction between these HO isoforms is the occurrence of heme regulatory motifs (HRMs) in HO2 that are lacking in HO1. The HRMs play a regulatory role as a thiol/disulfide redox switch that we have shown to regulate interactions of HO2 with substrate (heme) and with a Ca++- activated high conductance potassium channel (the BK or Slopoke channel). Regulation of K+ flux across the membrane by the BK channel enables the O2 sensing function of the carotid body, which controls respiratory system ventilation in response to changes in the blood oxygen concentration. We recently demonstrated that the BK channel also contains a thiol/disulfide redox switch that regulates binding of heme, which has been shown to control its K+ channel activity. We plan to use spectroscopic, kinetic, genetic, crystallographic, NMR, and electrophysiology methods to determine how these thiol/disulfide redox switches (the HRMs in human HO2 and the CXXC motif in the human BK channel) affect the structure and function of and interactions between these functionally linked proteins. We will determine the redox states of the heme and HRMs in vitro and in vivo under various physiological conditions. We also will perform spectroscopic and electrophysiology measurements to determine the mechanism by which HO2 influences BK channel function.