Spectroscopic studies reveal that the heme regulatory motifs of heme oxygenase-2 are dynamically disordered and exhibit redox-dependent interaction with heme.
Spectroscopic studies reveal that the heme regulatory motifs of heme oxygenase-2 are dynamically disordered and exhibit redox-dependent interaction with heme.
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DOI：
10.1021/bi501489r
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发表时间：
2015-05-05
期刊：
影响因子：
2.9
通讯作者：
Ragsdale, Stephen W.
中科院分区：
文献类型：
--
作者：
Bagai, Ireena;Sarangi, Ritimukta;Fleischhacker, Angela S.;Sharma, Ajay;Hoffman, Brian M.;Zuiderweg, Erik R. P.;Ragsdale, Stephen W.
血红素加氧酶（HO）催化血红素稳态的关键步骤：血红素通过O2-和NADPH-细胞色素P450还原酶依赖性转化为胆绿素、Fe和CO，其中血红素作为辅基和底物参与该过程。哺乳动物含有这种酶的两种同种型，HO 2和HO 1，它们共享形成催化核心和血红素结合位点的相同α-螺旋折叠，以及在它们的C-末端的跨膜螺旋。然而，与HO 1不同，HO 2具有额外的30个残基的N-末端以及位于血红素调节基序（HRM）中的C-末端附近的两个半胱氨酸-脯氨酸序列。虽然HO 2的额外的N-末端残基的作用还不清楚，但已经提出HRM可逆地形成硫醇/二硫化物氧化还原开关，其调节HO 2对铁血红素的亲和力作为细胞氧化还原平衡的函数。为了进一步定义HO 2特有的N-和C-末端区域的作用，我们使用多种光谱技术来表征人HO 2的这些区域。核磁共振光谱实验表明，当HRM是在氧化态（HO 2 O），额外的N-末端和C-末端HRM包含区域是无序的。然而，蛋白质NMR实验表明，在还原条件下，C-末端区域获得一些结构的Cys残基在HRM进行还原（HO 2 R），并在实验中采用抗磁性原卟啉，表明氧化还原依赖的核心和HRM域之间的相互作用。此外，电子核双共振和X-射线吸收光谱研究表明，在减少的HRM的巯基形式，半胱氨酸残基从HRM区域连接到一个铁血红素。结合EPR测量，其显示在还原的HO 2中出现新的低自旋血红素信号，似乎HRM中的半胱氨酸残基直接与第二结合血红素相互作用。
Heme oxygenase (HO) catalyzes a key step in heme homeostasis: the O2- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, and CO through a process in which the heme participates both as a prosthetic group and as a substrate. Mammals contain two isoforms of this enzyme, HO2 and HO1, which share the same α-helical fold forming the catalytic core and heme binding site, as well as a membrane spanning helix at their C-termini. However, unlike HO1, HO2 has an additional 30-residue N-terminus as well as two cysteine-proline sequences near the C-terminus that reside in heme regulatory motifs (HRMs). While the role of the additional N-terminal residues of HO2 is not yet understood, the HRMs have been proposed to reversibly form a thiol/disulfide redox switch that modulates the affinity of HO2 for ferric heme as a function of cellular redox poise. To further define the roles of the N- and C-terminal regions unique to HO2, we used multiple spectroscopic techniques to characterize these regions of the human HO2. Nuclear magnetic resonance spectroscopic experiments with HO2 demonstrate that, when the HRMs are in the oxidized state (HO2O), both the extra N-terminal and the C-terminal HRM-containing regions are disordered. However, protein NMR experiments illustrate that, under reducing conditions, the C-terminal region gains some structure as the Cys residues in the HRMs undergo reduction (HO2R) and, in experiments employing a diamagnetic protoporphyrin, suggest a redox-dependent interaction between the core and the HRM domains. Further, electron nuclear double resonance and X-ray absorption spectroscopic studies demonstrate that, upon reduction of the HRMs to the sulfhydryl form, a cysteine residue from the HRM region ligates to a ferric heme. Taken together with EPR measurements, which show the appearance of a new low-spin heme signal in reduced HO2, it appears that a cysteine residue(s) in the HRMs directly interacts with a second bound heme.
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影响因子：
15
作者：
Davydov, Roman;Sudhamsu, Jawahar;Hoffman, Brian M.
通讯作者：
Hoffman, Brian M.
影响因子：
3.7
作者：
DELEON, JM;REHR, JJ;ALBERS, RC
通讯作者：
ALBERS, RC
影响因子：
2.7
作者：
DELAGLIO, F;GRZESIEK, S;BAX, A
通讯作者：
BAX, A
DOI：
10.1046/j.1432-1327.1999.00677.x
发表时间：
1999-09-01
期刊：
EUROPEAN JOURNAL OF BIOCHEMISTRY
影响因子：
--
作者：
Ding, Y;McCoubrey, WK;Maines, MD
通讯作者：
Maines, MD
影响因子：
3
作者：
Gardner, Jessica D.;Yi, Li;Brunold, Thomas C.
通讯作者：
Brunold, Thomas C.