Photosynthetic reaction centers (RC) catalyze the conversion of light to chemical energy that supports life on Earth, but they exhibit substantial diversity among different phyla. This is exemplified in a recent structure of the RC from an anoxygenic green sulfur bacterium (GsbRC) which has characteristics that may challenge the canonical view of RC classification. The GsbRC structure is analyzed and compared with other RCs, and the observations reveal important but unstudied research directions that are vital for disentangling RC evolution and diversity. Namely, (1) common themes of electron donation implicate a Ca²⁺ site whose role is unknown; (2) a previously unidentified lipid molecule with unclear functional significance is involved in the axial ligation of a cofactor in the electron transfer chain; (3) the GsbRC features surprising structural similarities with the distantly-related photosystem II; and (4) a structural basis for energy quenching in the GsbRC can be gleaned that exemplifies the importance of how exposure to oxygen has shaped the evolution of RCs. The analysis highlights these novel avenues of research that are critical for revealing evolutionary relationships that underpin the great diversity observed in extant RCs.

光合反应中心 (RC) 催化光转化为支持地球生命的化学能，但它们在不同门之间表现出显着的多样性。这在最近来自无氧绿色硫细菌 (GsbRC) 的 RC 结构中得到了例证，其特征可能挑战 RC 分类的规范观点。对 GsbRC 结构进行分析并与其他 RC 进行比较，观察结果揭示了重要但未研究的研究方向，这对于解开 RC 进化和多样性至关重要。即，(1) 电子捐赠的共同主题涉及 Ca ²⁺角色未知的站点；(2) 以前未鉴定的功能意义不明的脂质分子参与了电子传递链中辅因子的轴向连接；(3) GsbRC 与远亲光系统 II 具有惊人的结构相似性；(4) 可以收集到 GsbRC 中能量猝灭的结构基础，这体现了暴露于氧气如何影响 RC 演变的重要性。该分析强调了这些新的研究途径，这些途径对于揭示支撑现存 RC 中观察到的巨大多样性的进化关系至关重要。