State Key Laboratory of Protein and Plant Genetic Engineering, School of Life Sciences, Peking University, Beijing, 100871, China.
State Key Laboratory of Membranes and Membrane Engineering, PKU-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China.
Photosynth Res. 2023 Nov;158(2):81-90. doi: 10.1007/s11120-023-01003-3. Epub 2023 Feb 27.
Gloeobacter violaceus is an ancient cyanobacterium as it branches out from the basal position in the phylogenic tree of cyanobacteria. It lacks thylakoid membranes and its unique bundle-shaped type of phycobilisomes (PBS) for light harvesting in photosynthesis are located on the interior side of cytoplasmic membranes. The PBS from G. violaceus have two large linker proteins that are not present in any other PBS, Glr2806, and Glr1262, which are encoded by the genes glr2806 and glr1262, respectively. The location and functions of the linkers Glr2806 and Glr1262 are currently unclear. Here, we report the studies of mutagenetic analysis of glr2806 and the genes of cpeBA, encoding the β and α subunits of phycoerythrin (PE), respectively. In the mutant lacking glr2806, the length of the PBS rods remains unchanged, but the bundles are less tightly packed as examined by electron microscopy with negative staining. It is also shown that two hexamers are missing in the peripheral area of the PBS core, strongly suggesting that the linker Glr2806 is located in the core area instead of the rods. In the mutant lacking the cpeBA genes, PE is no longer present and the PBS rods have only three layers of phycocyanin hexamers. The construction of deletional mutants in G. violaceus, achieved for the first time, provides critical information for our understanding of its unique PBS and should be useful in studies of other aspects of this interesting organism as well.
类球红细菌是古老的蓝细菌，因为它在蓝细菌的系统发育树中处于基础位置。它缺乏类囊体膜，其光合作用中用于收集光的独特束状藻胆体（PBS）位于质膜的内侧。来自类球红细菌的 PBS 有两个大的连接蛋白，它们不存在于任何其他 PBS 中，即 Glr2806 和 Glr1262，它们分别由基因 glr2806 和 glr1262 编码。连接蛋白 Glr2806 和 Glr1262 的位置和功能目前尚不清楚。在这里，我们报告了 glr2806 基因和编码藻红蛋白（PE）β和α亚基的 cpeBA 基因的突变分析研究。在缺乏 glr2806 的突变体中，PBS 棒的长度保持不变，但电子显微镜负染色检查显示束的组装不那么紧密。还表明，PBS 核心的外围区域缺少两个六聚体，强烈表明连接蛋白 Glr2806 位于核心区域而不是棒状结构中。在缺乏 cpeBA 基因的突变体中，PE 不再存在，PBS 棒只有三层藻蓝蛋白六聚体。首次在类球红细菌中构建缺失突变体，为我们理解其独特的 PBS 提供了关键信息，也应该对研究该有趣生物体的其他方面有用。
