The reaction center (RC) from the phototrophic bacterium Blastochloris viridis was the first integral membrane protein complex to have its structure determined by X-ray crystallography and has been studied extensively since then. It is composed of four protein subunits, H, M, L, and C, as well as cofactors, including bacteriopheophytin (BPh), bacteriochlorophyll (BCh), menaquinone, ubiquinone, heme, carotenoid, and Fe. In this study, we utilized mass spectrometry-based proteomics to study this protein complex via bottom-up sequencing, intact protein mass analysis, and native MS ligand-binding analysis. Its primary structure shows a series of mutations, including an unusual alteration and extension on the C-terminus of the M-subunit. In terms of quaternary structure, proteins such as this containing many cofactors serve to test the ability to introduce native-state protein assemblies into the gas phase because the cofactors will not be retained if the quaternary structure is seriously perturbed. Furthermore, this specific RC, under native MS, exhibits a strong ability not only to bind the special pair but also to preserve the two peripheral BCh’s.

中文翻译：

---

紫色光养细菌绿色芽绿藻反应中心的一级和高级结构：天然质谱测试


来自光养细菌绿色芽绿藻的反应中心 (RC) 是第一个通过 X 射线晶体学确定其结构的完整膜蛋白复合物，此后得到了广泛的研究。它由四个蛋白质亚基 H、M、L 和 C 以及辅助因子组成，包括细菌脱镁叶绿素 (BPh)、细菌叶绿素 (BCh)、甲基萘醌、泛醌、血红素、类胡萝卜素和 Fe。在这项研究中，我们利用基于质谱的蛋白质组学，通过自下而上测序、完整蛋白质质量分析和天然 MS 配体结合分析来研究这种蛋白质复合物。其一级结构显示出一系列突变，包括 M 亚基 C 末端的异常改变和延伸。就四级结构而言，诸如此类含有许多辅因子的蛋白质用于测试将天然状态蛋白质组装体引入气相的能力，因为如果四级结构受到严重扰动，辅因子将不会被保留。此外，这种特定的 RC 在天然 MS 下不仅表现出强大的能力，不仅能够结合特殊的配对，而且还能保留两个外围 BCh's。