海洋细菌应答DMSP趋化作用的受体鉴定和互作识别机制

DMSP is the most abundant sulfur-containing organic compound in the marine environment. Marine microbe breaks it down to dimethylsulfide, and release it into the atmosphere. The emitted DMS can act as cloud condensation nuclei, leading to an increasing amount of sunlight reflected back into space, and then affect the global climate. However, the biological function of this reaction for the marine microbes is still unknown. Based on our previous study on Alcaligenes faecalis J481 DMSP lyase knockout mutant showed lost the chemotaxis response to DMSP. This result reveals that DMS is the key signal molecule in the A. faecalis J481 DMSP chemotaxis process. To this end, in this proposal, we attempt to identify the chemoreceptor gene which could recognize DMS from 8 chemoreceptor genes in the A. faecalis J481 genome. And identify the interaction between the receptor and the DMS molecule. Also important is to identify the kinetics data of the receptor-ligand interaction. And also the subcellular localization of the receptor and structure detail analysis based on receptor-ligand co-crystallization. This study will reveal the molecular mechanism interaction between DMS and the receptor during A. faecalis J481 chemotaxis to DMSP. And also provide examples for us to understand DMSP and DMSP lyases in vivo function in the marine environment.

β-二甲基巯基丙酸（DMSP）是海洋环境中重要的含硫有机化合物，会被海洋中的微生物降解并释放出挥发性气体二甲基硫醚(DMS)。DMS进入大气层后可以作为云凝结核，提高云层反射率和降水，进而影响全球气候。然而目前关于该酶促过程的生物学意义所知甚少。在前期研究中发现，粪产碱菌J481中DMSP裂解酶基因dddY的缺失突变株表现出失去对DMSP的趋化作用。表明，DMS是该菌株中对DMSP趋化作用过程中的关键信号分子。本研究拟从8个候选基因中鉴定出该菌株中识别DMS的趋化受体基因，并且通过荧光热变分析法、等温滴定微量热法、蛋白的亚细胞定位以及蛋白质晶体结构解析等方法深入研究受体蛋白与DMS的相互作用机制。本项目的研究结果将解释DMSP趋化作用过程中信号分子DMS与受体的相互作用及其分子机制，同时完善我们对DMSP以及DMSP裂解酶在海洋微生物细胞内的功能。

β-二甲基巯基丙酸（DMSP）是海洋环境中重要的含硫有机化合物，会被海洋中的微生物降解并释放出挥发性气体二甲基硫醚(DMS)。DMS进入大气层后可以作为云凝结核，提高云层反射率和降水，进而影响全球气候。然而目前关于该酶促过程的生物学意义所知甚少。..本研究通过基因组挖掘，从粪产碱菌J481中一共找到了8个趋化受体基因。通过构建双交换敲除菌株以及回补，我们首次鉴定了细菌中能够识别DMS的趋化受体基因。并且通过荧光热变分析以及等温滴定微量热法研究了该受体蛋白与DMS的相互作用机制。本研究结果解释了DMSP趋化作用过程中信号分子DMS与受体的相互作用及其分子机制，同时帮助我们理解对DMSP以及DMSP裂解酶在海洋微生物细胞内的功能。