Phosphatidylglycerol is involved in the dimerization of photosystem II
Phosphatidylglycerol is involved in the dimerization of photosystem II
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DOI：
10.1074/jbc.275.9.6509
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发表时间：
2000-03-03
影响因子：
4.8
通讯作者：
Barber, J
中科院分区：
文献类型：
--
作者：
Kruse, O;Hankamer, B;Barber, J
通过蔗糖密度梯度分离由 CP47、CP43、D1 和 D2 蛋白、外在 33-kDa 亚基和低分子量多肽 PsbE、PsbF、PsbH、PsbI、PsbK、PsbL、PshTc 和 PsbW 组成的光系统 II 核心二聚体 (450 kDa) 和单体 (230 kDa)离心。光系统 II 核心二聚体用磷脂酶 A2 (PL-A2) 处理，该酶在 sn-2 位点切割磷脂酰甘油 (PG) 和磷脂酰胆碱分子。 PL-A2 处理的二聚体解离成两个核心单体，并进一步产生 CP47-D1-D2 亚复合物和 CP43。薄层色谱显示，光系统 II 二聚体的 PG 含量是其单体对应物的四倍，但磷脂酰胆碱水平相似。与此一致的是，与单体相比，二聚体含有更高水平的反式十六烷脂肪酸（C16:1 Delta 3tr），这是类囊体膜的 PG 所特有的。此外，与未处理的二聚体相比，用 PL-A2 处理二聚体增加了这种 PG 特异性脂肪酸的游离水平。重组实验进一步证明 PG 参与稳定光系统 II 的二聚体状态。使用尺寸排阻色谱法，结果表明，含有 C16:1 Delta 3tr 的 PG（而非其他脂质类别）可诱导分离的光系统 II 单体的显着二聚化。此外，当单体重构为含有 PG 的类囊体脂质时，通过电子晶体学观察到这种二聚化。重构二聚体的晶胞参数、p2 对称轴和投影图与天然二聚体的二维晶体观察到的相似。
Photosystem II core dimers (450 kDa) and monomers (230 kDa) consisting of CP47, CP43, the D1 and D2 proteins, the extrinsic 33-kDa subunit, and the low molecular weight polypeptides PsbE, PsbF, PsbH, PsbI, PsbK, PsbL, PshTc, and PsbW were isolated by sucrose density gradient centrifugation. The photosystem II core dimers were treated with phospholipase A2 (PL-A2), which cuts phosphatidylglycerol (PG) and phosphatidylcholine molecules at the sn-2 position. The PL-A2-treated dimers dissociated into two core monomers and further, yielding a CP47-D1-D2 subcomplex and CP43. Thin layer chromatography showed that photosystem II dimers contained four times more PG than their monomeric counterparts but with similar levels of phosphatidylcholine. Consistent with this was the finding that, compared with monomers, the dimers contained a higher level of trans-hexadecanoic fatty acid (C16:1 Delta 3tr), which is specific to PG of the thylakoid membrane. Moreover, treatment of dimers with PL-A2 increased the free level of this fatty acid specific to PG compared with untreated dimers. Further evidence that PG is involved in stabilizing the dimeric state of photosystem II comes from reconstitution experiments. Using size exclusion chromatography, it was shown that PG containing C16:1 Delta 3tr, but not other lipid classes, induced significant dimerization of isolated photosystem II monomers. Moreover, this dimerization was observed by electron crystallography when monomers were reconstituted into thylakoid lipids containing PG. The unit cell parameters, p2 symmetry axis, and projection map of the reconstituted dimer was similar to that observed for two dimensional crystals of the native dimer.