Elucidation of the Role of the Heme Regulatory Motif in Heme Oxygenase-2

描述（由申请人提供）：血红素加氧酶催化血红素转化为胆绿素、CO和铁。血红素加氧酶的两种形式（血红素加氧酶-1和血红素加氧酶-2）具有相似的物理和动力学性质，但表现出不同的生理作用和器官定位。血红素加氧酶-2和Ca激活的高电导钾通道（BK或Slopoke通道）之间的联系强烈地涉及响应于血氧浓度变化的颈动脉体的通气控制。血红素加氧酶-1和血红素加氧酶-2的序列之间的主要明显区别是血红素加氧酶-2中血红素响应（或调节）基序（HRM）的出现。已经提出血红素与HRM的相互作用来控制几种调节蛋白的活性或稳定性。基于最近的结果，HRM不结合血红素本身或影响HO-2的稳定性，但似乎充当参与调节血红素加氧酶-2对血红素的亲和力和铁血红素的自旋状态的氧化还原开关。我们计划使用光谱，动力学，分子遗传学和电生理学研究，以确定的作用，HRM在控制血红素加氧酶-2的结构和功能。我们将通过光谱和动力学方法表征血红素加氧酶-2中的血红素和HRM硫醇/二硫化物氧化还原中心，并在各种生理条件下在体外和体内确定HRM的氧化还原状态。我们还将进行光谱和电生理学测量，以确定血红素加氧酶-2影响BK通道功能的机制。血红素加氧酶是唯一已知能降解血红素的哺乳动物蛋白质，并位于几个主要氧化还原和金属调节系统的连接处。血红素加氧酶-2（HO-2）的C-末端的两个血红素调节基序将其与血红素加氧酶-1区分开。该提案旨在确定这些血红素调节基序如何调节HO-2的酶和调节特性。

DESCRIPTION (provided by applicant): Heme oxygenase catalyzes the conversion of heme to biliverdin, CO, and iron. The two forms of heme oxygenase (heme oxygenase-1 and heme oxygenase-2) share similar physical and kinetic properties but exhibit different physiological roles and organ locations. The linkage between heme oxygenase-2 and a Caactivated high conductance potassium channel (the BK or Slopoke channel) has been strongly implicated in the control of ventilation by the carotid body in response to changes in the blood oxygen concentration. The major apparent distinction between the sequences of heme oxygenase-1 and heme oxygenase-2 is the occurrence of heme responsive (or regulatory) motifs (HRMs) in heme oxygenase-2. The interaction of heme with HRMs has been proposed to control the activity or stability of several regulatory proteins. Based on recent results, HRM does not bind heme per se or affect HO-2 stability, but appears to act as a redox switch involved in regulating the affinity of heme oxygenase-2 for heme and the spin state of the ferric heme. We plan to use spectroscopic, kinetic, molecular genetic, and electrophysiology studies to determine the role of the HRM in controlling heme oxygenase-2 structure and function. We will characterize the heme and HRM thiol/disulfide redox centers in heme oxygenase-2 by spectroscopic and kinetic methods and determine the redox state of the HRM in vitro and in vivo under various physiological conditions. We also will perform spectroscopic and electrophysiology measurements to determine the mechanism by which heme oxygenase-2 influences BK channel function. PUBLIC HEALTH RELEVANCE Heme oxygenase is the only mammalian protein known to degrade heme and sits at the nexus of several major redox and metal regulatory systems. Two Heme Regulatory Motifs at the C- terminal end of heme oxygenase-2 (HO-2) differentiate it from heme oxygenase-1. This proposal is aimed at determining how(s) these Heme Regulatory Motifs regulate the enzymatic and regulatory properties of HO-2.