The solution structure of photosystem I accessory protein E from the cyanobacterium Nostoc sp. strain PCC 8009.
The solution structure of photosystem I accessory protein E from the cyanobacterium Nostoc sp. strain PCC 8009.
复制标题
蓝藻发菜光系统 I 辅助蛋白 E 的溶液结构。
DOI：
10.1021/bi9910373
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发表时间：
1999
期刊：
影响因子：
2.9
通讯作者：
Falzone,CJ
中科院分区：
文献类型：
--
作者：
Mayer,KL;Shen,G;Bryant,DA;Lecomte,JT;Falzone,CJ
PsaE是位于光系统I基质（细胞质）侧的小的碱性亚基。在蓝细菌中，该亚基参与循环电子传递并调节复合物与可溶性铁氧还蛋白的相互作用。从蓝细菌Synechococcussp.中分离的PsaE蛋白。菌株PCC 7002采用SH 3结构域的β拓扑结构，具有五条β链（βA至βE）和链βD和βE之间的310螺旋转角[Falzone，C. J.，考，Y.- H、赵，J，Bryant，D.一、和Lecomte，J.T. J.（1994）Biochemistry33，6052 - 6062]。PsaE蛋白的一级结构在所有放氧光合生物中是高度保守的。然而，环长度的可变性，以及N-或C-末端延伸，表明第二个代表性PsaE亚基的结构将是有用的，以表征光系统I多肽之间的相互作用。在这项工作中，解决方案的结构PsaE从蓝藻Nostocsp。菌株PCC 8009通过NMR方法确定。与聚球藻PsaE相比，在菌株PCC 7002中，该PsaE在连接链βC和βD的环中具有7个残基缺失，以及8个残基的C端延伸。来自homestructive和heterestructive NMR实验的角度和距离的限制被用来计算的距离几何/模拟退火协议的结构。一个家庭的20个结构（rmsd为0.24 μ m的规则二级结构）。这两种蓝藻蛋白之间的差异主要局限于CD环区域; C-末端延伸是无序的。对念珠藻的热力学稳定性进行了研究。通过圆二色性和荧光光谱测定菌株PCC 8009 PsaE对尿素变性，并通过UV吸收光谱监测热变性。化学和热变性曲线满意地模拟与两个状态的过程。室温下解折叠的ΔG°为12.4 ± 0.3 kJ mol-1（pH 5），热转变中点为59 ± 1 °C（pH 7）。与光系统I复合物中的其他蛋白质的相互作用可能有助于在生理条件下维持PsaE在其天然状态。
PsaE is a small basic subunit located on the stromal (cytoplasmic) side of photosystem I. In cyanobacteria, this subunit participates in cyclic electron transport and modulates the interactions of the complex with soluble ferredoxin. The PsaE protein isolated from the cyanobacteriumSynechococcussp. strain PCC 7002 adopts the β topology of an SH3 domain, with five β strands (βA through βE) and a turn of 310helix between strands βD and βE [Falzone, C. J., Kao, Y.-H., Zhao, J., Bryant, D. A., and Lecomte, J. T. J. (1994)Biochemistry33, 6052−6062]. The primary structure of the PsaE protein is strongly conserved across all oxygen-evolving photosynthetic organisms. However, variability in loop lengths, as well as N- or C-terminal extensions, suggests that the structure of a second representative PsaE subunit would be useful to characterize the interactions among photosystem I polypeptides. In this work, the solution structure of PsaE from the cyanobacteriumNostocsp. strain PCC 8009 was determined by NMR methods. Compared to PsaE fromSynechococcussp. strain PCC 7002, this PsaE has a seven-residue deletion in the loop connecting strands βC and βD, and an eight-residue C-terminal extension. Angular and distance restraints derived from homonuclear and heteronuclear NMR experiments were used to calculate structures by a distance-geometry/simulated-annealing protocol. A family of 20 structures (rmsd of 0.24 Å in the regular secondary structure) is presented. Differences between the two cyanobacterial proteins are mostly confined to the CD loop region; the C-terminal extension is disordered. The thermodynamic stability ofNostocsp. strain PCC 8009 PsaE toward urea denaturation was measured by circular dichroism and fluorescence spectroscopy, and thermal denaturation was monitored by UV absorption spectroscopy. Chemical and thermal denaturation curves are modeled satisfactorily with two-state processes. The ΔG° of unfolding at room temperature is 12.4 ± 0.3 kJ mol-1(pH 5), and the thermal transition midpoint is 59 ± 1 °C (pH 7). Interactions with other proteins in the photosystem I complex may aid in maintaining PsaE in its native state under physiological conditions.