Sulfide Oxidation and Signaling

硫化氢(H2S)是一种能引起深刻生理效应的信号分子。 哺乳动物硫代谢的产物，合成速率相对较高。硫化氢 是由硫磺网络中的三种酶生物合成的，其中两种，胱硫醚-β- 合成酶(CBS)和γ-胱硫酶，存在于细胞质的转硫酶中 途径，而第三个，硫代丙酮酸硫基转移酶参与半胱氨酸 分解代谢。由于硫化氢毒性很大，细胞通过有效的氧化来避免其积聚。 位于线粒体中并与产生能量的电子相耦合的途径 传送链。组成蛋白包括硫代苯醌氧化还原酶，a 过硫化物双加氧酶、锰氧化物和亚硫酸盐氧化酶。而我们对硫化氢的研究 HL58784支持生物发生，我们在硫化氢氧化和信号转导方面的工作是 由GM130183支持。越来越明显的是，生物合成和 硫化氢的分解代谢途径相互作用、相互调节。因此，硫化物 由HL58784支持的研究将于今年到期，将被并入并随后 正式包含在GM130183的竞争更新中。在这个补充项目中， 以下具体目标将用于阐明以下基本机制 CBS在正常和疾病状态下对H_2S合成的调节：I)阐明 CBS中接头突变体在正则硫化和非正则硫化过程中的状态动力学 生成硫化氢的反应，(Ii)用EPR研究血红素环境中的扰动 光谱和电位滴定，(Iii)评估突变对 ADOMet依赖的CO和NO·与亚铁血红素结合及对细胞的调节作用 硫磺的助熔剂，以及(Iv)结晶看起来不太容易 与野生型CBS相比，聚集。拟议研究的影响将是 基础(即阐明CBS和In水平上的变构调节机制 途径)、医学(即了解疾病失败的生化基础-- 造成CBS突变)，最重要的是，培养一位有希望的URM科学家。

Hydrogen sulfide (H2S), a signaling molecule that elicits profound physiological effects, is a product of mammalian sulfur metabolism and is synthesized at relatively high rates. H2S is biosynthesized by three enzymes in the sulfur network of which two, cystathionine beta- synthase (CBS) and gamma-cystathionase, reside in the cytoplasmic transsulfuration pathway while the third, mercaptopyruvate sulfurtransferase, is involved in cysteine catabolism. Since H2S is highly toxic, cells avoid its build-up by an efficient oxidation pathway that is housed in mitochondria and coupled to the energy-generating electron transfer chain. The constituent proteins include sulfide-quinone oxidoreductase, a persulfide dioxygenase, rhodanese and sulfite oxidase. While our studies on H2S biogenesis are supported by HL58784, our work on H2S oxidation and signaling are supported by GM130183. It is becoming increasing clear that the biosynthetic and catabolic pathways for H2S interact and modulate each other. Therefore, the sulfide research supported by HL58784, scheduled to expire this year, will be folded into and then formally included in the competitive renewal of GM130183. In this supplemental project, the following specific aims will be addressed to elucidate fundamental mechanisms of regulation of H2S synthesis by CBS in normal and disease states: i) elucidate the steady state kinetics of linker mutants in CBS in the canonical transsulfuration and non-canonical H2S-generating reactions, (ii) investigate perturbations in the heme environment by EPR spectroscopy and potentiometric titrations, (iii) assess the impact of the mutations on AdoMet-dependent modulation of CO and NO• binding to ferrous heme and on the cellular flux of sulfur, and (iv) crystallize the linker mutants that appear to be less prone to aggregation compared to wild-type CBS. The impact of the proposed studies will be fundamental (i.e. elucidating mechanims of allosteric regulation at the level of CBS and in the pathway), medical (i.e. understanding the biochemical basis of failure of disease- causing CBS mutations), and most importantly, training a URM scientist of high promise.