Structure and mechanistic studies of the bacterial organomercurial lyase MerB

含汞化合物通过自然事件或人类活动引入环境，包括火山、海洋排放、化石燃料燃烧、牙科汞齐和金矿开采。鉴于含汞化合物的毒性，汞污染是一个极其重要的环境问题，在剧毒甲基汞集中的水域沉积物中尤其危险。从历史上看，通过物理或化学修复来清理被汞污染的沉积物的努力一直受到这样一个事实的阻碍，即这些程序成本高昂，而且对环境造成破坏。因此，开发一种生物修复系统来处理汞污染一直是人们关注的焦点。这种方法不仅更具成本效益，而且对自然生态系统的破坏也更少。抗汞细菌已经开发出一种由两种酶(MERA和MerB)组成的系统，使它们能够通过将离子汞和有机汞化合物转化为元素汞来有效地解毒。鉴于这两种酶的独特性质，它们是用于清理汞污染沉积物的生物修复系统的理想选择。例如，转化了产生MERA和MerB酶的基因的植物或树木可以在有毒水平的离子汞或甲基汞存在下生长。当这些转基因植物和树木暴露在甲基汞中时，它们提取甲基汞并释放出毒性较低的元素汞。元素汞在大气中的停留时间约为两年，因此很容易稀释到痕量浓度，然后重新沉积到陆地和深海沉积物中。我们项目的目标是更好地了解MERA和MerB的功能，以便更好地将它们用于生物修复，如清理甲基汞污染沉积物的植物修复系统。

Mercury-containing compounds are introduced into the environment from either natural occurrences or human activity including volcanoes, oceanic emissions, combustion of fossil fuels, dental amalgams, and gold mining. Given the toxicity of mercury-containing compounds, mercury contamination is an extremely important environmental problem, and it is particularly hazardous in aquatic sediments where the highly toxic methylmercury concentrates. Historically, attempts to clean up mercury-contaminated sediments by either physical or chemical remediation have been hampered by the fact that these procedures are expensive and environmentally destructive. As a result, there has been a great deal of focus to develop a bioremediation system to deal with mercury contamination. Such an approach is not only more cost effective but also less disruptive to the natural ecosystems. Mercury-resistant bacteria have developed a system of two enzymes (MerA and MerB) that allows them to efficiently detoxify both ionic and organic mercury compounds by converting them to elemental mercury. Given the unique qualities of these two enzymes, they are ideally for use in bioremediation systems designed for cleaning up mercury-contaminated sediments. For example plants or trees transformed with the genes that produce the MerA and MerB enzymes can grow in the presence of toxic levels of either ionic mercury or methylmercury. When exposed to methylmercury, these transgenic plants and trees extract the MeHg and transpire the less toxic elemental mercury The atmospheric residence time of elemental mercury is about two years, thus it can easily be diluted to trace concentrations before redepositing into terrestrial and deep oceanic sediments. The goal of our project is to better understand the function of MerA and MerB so that they can be better used in bioremediation such as the phytoremediation system for the clean up of methylmercury-contaminated sediments.