Distinguishing Nitro vs Nitrito Coordination in Cytochrome c' Using Vibrational Spectroscopy and Density Functional Theory.
Distinguishing Nitro vs Nitrito Coordination in Cytochrome c' Using Vibrational Spectroscopy and Density Functional Theory.
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DOI：
10.1021/acs.inorgchem.7b01945
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发表时间：
2017-11-06
影响因子：
4.6
通讯作者：
Andrew CR
中科院分区：
文献类型：
--
作者：
Nilsson ZN;Mandella BL;Sen K;Kekilli D;Hough MA;Moënne-Loccoz P;Strange RW;Andrew CR
亚硝酸盐与血红素辅因子的配位是信号分子一氧化氮（NO）厌氧产生的关键步骤。作为一种双齿配体，亚硝酸根有可能通过N-（硝基）或O-（亚硝酸根）原子以可以指导其反应性的方式进行配位。因此，区分硝基与亚硝酸根配位，沿着周围蛋白质的影响，是特别感兴趣的。在这项研究中，我们探讨了铁（III）血红素亚硝酸盐协调在Alcaligenes xylosoxidans细胞色素c′（AXCP），一个NO载体，排除阴离子在其天然状态下，但很容易结合亚硝酸盐（Kd值为0.5 mM）后，远端Leu 16 → Gly突变，以消除远端空间限制。室温共振拉曼光谱（407 nm激发）识别溶液中的ν（Fe-NO2）、δ（ONO）和νs（NO2）亚硝酸根配体振动。用351 nm紫外光照射导致光转化为{FeNO}6和{FeNO}7状态，使得FTIR测量能够从差分光谱中区分νs（NO2）和νas（NO2）振动。密度泛函理论计算突出血红素环境，亚硝酸盐的配位模式，和振动特性之间的连接，并确认亚硝酸盐绑定到L16 G AXCP只通过N原子。获得亚硝酸盐络合物晶体结构的努力受到X射线束中光化学的阻碍。虽然低剂量的晶体结构可以模拟与混合亚硝酸盐（硝基）/H2O远端人口，其光敏性和部分占用强调的振动方法的价值。总体而言，这项研究揭示了血红素亚硝酸盐结合的空间决定因素，并为未来的血红素蛋白亚硝酸盐反应的研究提供了振动基准。
Nitrite coordination to heme cofactors is a key step in the anaerobic production of the signaling molecule nitric oxide (NO). An ambidentate ligand, nitrite has the potential to coordinate via the N- (nitro) or O- (nitrito) atoms in a manner that can direct its reactivity. Distinguishing nitro vs nitrito coordination, along with the influence of the surrounding protein, is therefore of particular interest. In this study, we probed Fe(III) heme-nitrite coordination in Alcaligenes xylosoxidans cytochrome c′ (AXCP), an NO carrier that excludes anions in its native state but that readily binds nitrite (Kd ∼ 0.5 mM) following a distal Leu16 → Gly mutation to remove distal steric constraints. Room-temperature resonance Raman spectra (407 nm excitation) identify ν(Fe–NO2), δ(ONO), and νs(NO2) nitrite ligand vibrations in solution. Illumination with 351 nm UV light results in photoconversion to {FeNO}6 and {FeNO}7 states, enabling FTIR measurements to distinguish νs(NO2) and νas(NO2) vibrations from differential spectra. Density functional theory calculations highlight the connections between heme environment, nitrite coordination mode, and vibrational properties and confirm that nitrite binds to L16G AXCP exclusively through the N atom. Efforts to obtain the nitrite complex crystal structure were hampered by photochemistry in the X-ray beam. Although low dose crystal structures could be modeled with a mixed nitrite (nitro)/H2O distal population, their photosensitivity and partial occupancy underscores the value of the vibrational approach. Overall, this study sheds light on steric determinants of hemenitrite binding and provides vibrational benchmarks for future studies of heme protein nitrite reactions.
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DOI：
10.1073/pnas.1522670113
发表时间：
2016-07-26
影响因子：
11.1
作者：
Corti, Paola;Xue, Jianmin;Gladwin, Mark T.
通讯作者：
Gladwin, Mark T.
影响因子：
2.9
作者：
He, Chunmao;Ogata, Hideaki;Knipp, Markus
通讯作者：
Knipp, Markus
影响因子：
15
作者：
Kurtikyan, Tigran S.;Hovhannisyan, Astghik A.;Ford, Peter C.
通讯作者：
Ford, Peter C.
影响因子：
4.3
作者：
Hopmann, Kathrin H.;Cardey, Bruno;Gladwin, Mark T.;Kim-Shapiro, Daniel B.;Ghosh, Abhik
通讯作者：
Ghosh, Abhik
DOI：
10.1016/j.niox.2013.11.002
发表时间：
2014-04-30
期刊：
Nitric oxide : biology and chemistry
影响因子：
--
作者：
Kim-Shapiro DB;Gladwin MT
通讯作者：
Gladwin MT