蓝细菌光合作用捕光复合物—藻胆体中核膜连接蛋白LCM的N端结构域的结构和功能研究

The Core-membrane linker polypeptide (LCM) is a key component in cyanobacterial phycobilisomes, playing a crucial role in the anchoring of the phycobilisome to the thylakoid membrane and the energy transfering from the phycobilisome to the photosynthetic reaction center. In this project, detailedly structural and functional studies on the N-terminal domain (pfam00502) of LCM will be conducted. First, by using crystallographic methods, crystal structure of chromophorylated pfam00502 will be solved to reveal the molecular basis for its function as the terminal energy acceptor. Secondly, through a molecular dynamic simulation, conformation of chromophores in the crystal structure of chromophorylated pfam00502 will be analyzed. Thirdly, through the mutation and dynamics studies, molecular mechanism for the auto-chromophorylation of pfam00502 will be elucidated. Finally, interaction between pfam00502 and other phycobiliproteins subunits in the cores of cyanobacterial phycobilisomes will be systematically studied to reveal how the phycobiliprotein subunits and pfam00502 interact with the chromophores and the dipole-dipole interaction in the terminal energy acceptor. Results from these studies will be greatly helpful in elucidating the molecular mechanism of supramolecular assembly and energy transfer process in cyanobacterial phycobilisomes and have an importantly theoretical significance.

本课题将以蓝细菌捕光复合物-藻胆体中核膜连接蛋白LCM为研究对象，重点研究其直接执行末端能量受体功能的N端pfam00502结构域的晶体结构、自色素化机制及与藻胆蛋白的相互作用。首先通过晶体学的方法解析色素化的pfam00502结构域的晶体结构，揭示其行使末端能量受体功能的结构基础；并通过分子动力学模拟对晶体结构中的色素分子进行分析，阐述其可能的构象变化；在此基础上，通过突变实验和动力学研究阐明pfam00502自催化色素化的分子机制；最后利用GST Pull-down 手段研究pfam00502同藻胆体核结构其他藻胆蛋白组分的相互作用，并以此为基础阐明末端能量受体中色素分子偶极-偶极相互作用。本项研究将填补蓝细菌（藻）藻胆体中核膜连接蛋白晶体结构研究的空白，有助于精确阐述藻胆体超分子体系的组装机制和能量传递过程，具有重要理论意义。

核膜连接蛋白LCM是藻胆体末端能量受体（TEA）的关键组成部分，对其进行结构和功能研究将有助于阐明藻胆体超分子体系组装及能量传递机制。本项目通过生化分析，计算模拟及突变实验，阐明了蓝藻LCM的N端结构域Pfam00502 （LP502）自色素化机制，并构建了PCB-LP502复合体的结构模型，分析了TEA中的偶极及其相互作用，最终提出了TEA的精细分子结构模型。另外，本项目还研究了极地蓝藻的藻胆体及藻胆蛋白的适冷机制，并研究了在缺氮过程中红藻类囊体膜超分子结构的变化。本项目还资助了海洋细菌多样性，新种鉴定及其产生的胞外多糖，有机质降解酶的性质等项研究。项目已资助发表SCI论文10篇。