State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan 250100, China.
Mol Microbiol. 2011 Nov;82(3):698-705. doi: 10.1111/j.1365-2958.2011.07844.x. Epub 2011 Oct 10.
Phycobilisomes are light-harvesting supramolecular complexes in cyanobacteria and red algae. Linkers play a pivotal role in the assembly and energy transfer modulation of phycobilisomes. However, how linkers function remains unclear due to the lack of structural and biochemical studies of linkers, especially the N-terminal domain of L(R) (pfam00427). Here, we report the crystal structure of the pfam00427 domain of the linker L(R) (30) from Synechocystis sp. PCC 6803 at 1.9 Å. The pfam00427 presents as a previously uncharacterized point symmetric six α-helix bundle. To elucidate the binding style of pfam00427 in the C-phycocyanin (C-PC) (αβ)(6) hexamer, we fixed pfam00427 computationally into the C-PC (αβ)(6) inner cavity using the program AutoDock. Combined with a conserved 'C-PC binding patch' on pfam00427 identified, we arrived at a model for the pfam00427-C-PC (αβ)(6) complex. This model was further optimized and evaluated as a reasonable result by a molecular dynamics simulation. In the resulting model, the pfam00427 domain is stably positioned in the central hole of the C-PC trimer. Moreover, the L(RT) (pfam01383) was docked into our pfam00427-C-PC model to generate a complete phycobilisome rod in which the linkers join individual biliprotein hexamers.
藻胆体是蓝细菌和红藻中的光捕获超分子复合物。接头在藻胆体的组装和能量转移调节中起着关键作用。然而，由于缺乏对接头的结构和生化研究，特别是 pfam00427 的 N 端结构域，接头的功能仍然不清楚。在这里，我们报道了来自集胞藻 PCC 6803 的接头 L(R)（30）的 pfam00427 结构域的晶体结构，分辨率为 1.9Å。 pfam00427 呈现为以前未表征的点对称六 α-螺旋束。为了阐明 pfam00427 在藻蓝蛋白（C-PC）（αβ）（6）六聚体中的结合方式，我们使用 AutoDock 程序将 pfam00427 固定在 C-PC（αβ）（6）内腔中。结合在 pfam00427 上鉴定的保守的“C-PC 结合斑块”，我们得到了 pfam00427-C-PC（αβ）（6）复合物的模型。通过分子动力学模拟对该模型进行了进一步优化和评估，结果合理。在得到的模型中，pfam00427 结构域稳定地位于 C-PC 三聚体的中心孔中。此外，将 L(RT)（pfam01383）对接入我们的 pfam00427-C-PC 模型中，生成了一个完整的藻胆体棒，其中接头将各个双蛋白六聚体连接在一起。
