The Influence of Cysteinate Protonation in Nickel Containing Metalloenzymes

半胱氨酸质子化对含镍金属酶的影响

• 批准号: 9170625
• 负责人: Jason M Shearer
• 金额: $ 22.16万
• 依托单位: UNIVERSITY OF NEVADA RENO
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9170625
• 关键词: Active Sites; Amino Acids; Biochemical; Biochemical Process; Biochemical Reaction; Bioinorganic Chemistry; Chemistry; Cleaved cell; Computational Technique; Coupled; Docking; Electron Transport; Electrons; Elements; Environment; Enzymes; Geometry; Health; Helicobacter pylori; Human; Hydrogen Bonding; Hydrogen Peroxide; Investigation; Iron; Lead; Length; Ligands; Metals; Microbe; Modeling; Nature; Nickel; Optics; Process; Property; Protons; Psychological Techniques; Reaction; Research; Resources; Roentgen Rays; Running; Series; Site; Spectrum Analysis; Structure; Superoxide Dismutase; System; Thermodynamics; Ursidae Family; Work; absorption; abstracting; analog; base; computer studies; electronic structure; geometric structure; human disease; insight; interest; metalloenzyme; nickel-iron hydrogenase; novel therapeutic intervention; oxidation; pathogen; pathogenic bacteria; physical property; protonation; small molecule; tool

Project Summary. Cysteinate ligated nickel metalloenzymes are found in a number of pathogenic bacteria. Some of these nickel containing metalloenzymes, such as nickel-iron hydrogenase ([NiFe]H2ase) found in Helicobacter pylori, are found in microbes responsible for human diseases. At least two nickel containing metalloenzymes, nickel containing superoxide dismutase (NiSOD) and [NiFe]H2ase, possess a coordinated protonated cysteinate residue (Ni-S(H+)-Cys). We suspect that the Ni-S(H+)-Cys bond is involved in the enzymatic mechanism and also modulates the electronic structure and reactivity of these metalloenzymes. Our research will take advantage of functional metalloenzyme based mimics of NiSOD and small molecule mimics of [NiFe]H2ase. Metallopeptide based mimics of NiSOD that my group has prepared to date reproduce the structure and physical properties of the metalloenzyme. These metallopeptides are also catalytically active, effecting O2– disproportionation with rate constants approaching those observed in the metalloenzyme. Recent work by my group has demonstrated that these mimics facilitate O2– reduction to H2O2 via a unique proton coupled electron transfer (PCET) reaction from a Ni-S(H+)-Cys moiety to O –. We will probe this reaction by 2 preparing derivatives of these metallopeptides that will alter the fundamental nature of the PCET reaction. This will yield insight into the general scope of PCET reactions facilitated by such moieties. In addition, we will prepare metallopeptide based NiSOD mimics that more accurately replicate the enzymatic reaction mechanism. Preliminary work demonstrates that the mechanism of O2– reduction effected by the metallopeptide is distinct from NiSOD itself. By producing mimics that reproduce enzymatic reactivity we will gain a better understanding of the mechanism of O2– disproportionation effected by NiSOD itself. Also, we will investigate the influence of the Ni-S(H+)-Cys moiety on [NiFe]H2ase model compounds. We propose that the protonation of the coordinated cysteinate ligand is dramatically altering the electronic structure of the Ni-center in [NiFe]-H2ase; specifically it is reducing the hydricity of the mechanistically important Ni(III)-H intermediate biasing [NiFe]H2ase to perform H2 oxidation chemistry. This supposition will also be probed under this initiative. This research runs the gamut of tools utilized in bioinorganic chemistry. As with many of our studies synthetic, biochemical, spectroscopic, mechanistic, and computational studies will be brought to bear on understanding all aspects of the metallopeptides and small molecule mimics. The use of metalloenzyme mimics in our investigations is especially noteworthy; few studies have been performed where insight into specific biochemical processes are revealed through metallopeptide based metalloenzyme mimics. Therefore completion of this project will not only reveal interesting aspects of biologically important Ni-S(H+)-Cys moieties, but will also push the limits of investigations concerning metallopeptide based metalloenzyme mimics.

项目摘要在​​许多病原菌中发现了半胱氨酸连接的镍金属酶。 其中一些含镍金属酶，例如镍铁氢化酶（[NiFe]H2ase） 幽门螺杆菌是导致人类疾病的微生物中至少含有两种镍。 金属酶、含镍超氧化物歧化酶 (NiSOD) 和 [NiFe]H2ase 具有协调性 我们怀疑 Ni-S(H+)-Cys 键参与了质子化的半胱氨酸残基 (Ni-S(H+)-Cys)。 酶机制，还调节这些金属酶的电子结构和反应性。 我们的研究将利用基于 NiSOD 和小分子的功能性金属酶模拟物 我的小组迄今为止已准备复制基于金属肽的 NiSOD 模拟物。 这些金属酶的结构和物理性质也具有催化活性， 影响 O2- 歧化的速率常数接近最近在金属酶中观察到的速率常数。 我的团队的工作表明，这些模拟物通过独特的质子促进 O2- 还原为 H2O2 从 Ni-S(H+)-Cys 部分到 O – 的耦合电子转移 (PCET) 反应我们将通过以下方式探究该反应。 2 制备这些金属肽的衍生物将改变 PCET 反应的基本性质。 将深入了解这些部分促进的 PCET 反应的一般范围。 制备基于金属肽的 NiSOD 模拟物，可以更准确地复制酶反应 初步工作表明O2-还原的机制是受O2-还原影响的。 金属肽与 NiSOD 本身不同，通过生产可重现酶反应性的模拟物，我们将能够实现这一点。 更好地了解 NiSOD 本身影响的 O2-歧化机制。 研究 Ni-S(H+)-Cys 部分对 [NiFe]H2ase 模型化合物的影响。 配位半胱氨酸配体的质子化极大地改变了镍中心的电子结构 在 [NiFe]-H2ase 中，它会降低机械上重要的 Ni(III)-H 中间体的水度 偏压 [NiFe]H2ase 进行 H2 氧化化学也将在该倡议下进行探讨。 与我们的许多合成研究一样，这项研究涵盖了生物无机化学中使用的所有工具。 生物化学、光谱、机械和计算研究将有助于理解 金属肽和小分子模拟物的各个方面在我们的应用中。 很少有研究深入了解具体情况； 通过基于金属肽的金属酶模拟物揭示生化过程。 该项目的完成不仅将揭示具有重要生物学意义的 Ni-S(H+)-Cys 的有趣方面 部分，但也将突破基于金属酶的金属肽研究的极限 模仿。