Thiol/Disulfide Redox Regulation of Heme Oxygenase-2

描述（由申请人提供）：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特性，但表现出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重叠的，这些HO亚型之间的主要区别是HO2中出现了HO1中缺乏的血红素调控基序（HRMs）。HRMs作为硫醇/二硫化物氧化还原开关发挥调节作用，我们已经证明它可以调节HO2与底物（血红素）和Ca++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K+通过膜的通量，实现颈动脉体的O2感应功能，从而根据血氧浓度的变化控制呼吸系统通气。我们最近证明BK通道还包含一个调节血红素结合的硫醇/二硫氧化还原开关，该开关已被证明可以控制其K+通道活性。我们计划使用光谱、动力学、遗传学、晶体学、核磁共振和电生理学方法来确定这些硫醇/二硫氧化还原开关（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蛋白的结构和功能以及它们之间的相互作用。我们将测定血红素和HRMs在体内和体外不同生理条件下的氧化还原状态。我们还将进行光谱和电生理学测量，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.