Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47906.
SSCI, a Division of Albany Molecular Research Inc., West Lafayette, Indiana 47906.
J Biol Chem. 2019 Nov 22;294(47):17758-17767. doi: 10.1074/jbc.RA119.009331. Epub 2019 Oct 9.
The photosynthetic cytochrome complex, a homodimer containing eight distinct subunits and 26 transmembrane helices per monomer, catalyzes proton-coupled electron transfer across the thylakoid membrane. The 2.5-Å-resolution structure of the complex from the cyanobacterium sp. revealed the presence of 23 lipid-binding sites per monomer. Although the crystal structure of the cytochrome from a plant source has not yet been solved, the identities of the lipids present in a plant complex have previously been determined, indicating that the predominant lipid species are monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), phosphatidylglycerol (PG), and sulfoquinovosyldiacylglycerol (SQDG). Despite the extensive structural analyses of -lipid interactions, the basis of the stabilization by lipids remains poorly understood. In the present study, we report on the effect of individual lipids on the structural and functional integrity of the complex, purified from It was found that (i) galactolipids (MGDG, DGDG, and SQDG) and phospholipids dilinolenoyl-phosphatidylglycerol (DLPG), 1,2-dioleoylphosphatidylglycerol (DOPG), and 1,2-dioleoyl--glycerol-3-phosphatidylcholine (DOPC) structurally stabilize the complex to varying degrees; (ii) SQDG has a major role in stabilizing the dimeric complex; (iii) the complex is stabilized by incorporation into nanodiscs or bicelles; (iv) removal of bound phospholipid by phospholipase A inactivates the cytochrome complex; and (v) activity can be restored significantly by the addition of the anionic lipid PG, which is attributed to stabilization of the quinone portal and the hinge region of the iron-sulfur protein.
光合作用细胞色素复合 物是一种同二聚体，每个单体包含八个不同的亚基和 26 个跨膜螺旋，催化质子偶联电子在类囊体膜中的转移。来自蓝藻 sp.的复合物的 2.5-埃分辨率结构揭示了每个单体存在 23 个脂质结合位点。尽管尚未解决来自植物源的细胞色素的晶体结构，但先前已经确定了植物复合物中存在的脂质，表明主要的脂质种类是单半乳糖二酰基甘油（MGDG）、双半乳糖二酰基甘油（DGDG）、磷脂酰甘油（PG）和硫酸奎诺二酰基甘油（SQDG）。尽管对-脂相互作用的广泛结构分析，但脂质稳定的基础仍知之甚少。在本研究中，我们报告了单个脂质对从 sp.纯化的 复合物的结构和功能完整性的影响。发现（i）半乳糖脂（MGDG、DGDG 和 SQDG）和磷脂二亚麻酰基磷脂酰甘油（DLPG）、1,2-二油酰基磷脂酰甘油（DOPG）和 1,2-二油酰基-甘油-3-磷酸胆碱（DOPC）在不同程度上结构稳定复合物；（ii）SQDG 在稳定二聚体复合物方面起主要作用；（iii）通过并入纳米盘或双分子层稳定细胞色素复合物；（iv）通过磷脂酶 A 去除结合的磷脂使细胞色素复合物失活；和（v）通过添加阴离子脂质 PG 可显著恢复活性，这归因于醌门户和铁硫蛋白铰链区域的稳定。
