Globins (Glbs) are widely distributed in archaea, bacteria and eukaryotes. They can be classified into proteins with 2/2 or 3/3 α‐helical folding around the heme cavity. Both types of Glbs occur in green algae, bryophytes and vascular plants. The Glbs of angiosperms have been more intensively studied, and several protein structures have been solved. They can be hexacoordinate or pentacoordinate, depending on whether a histidine is coordinating or not at the sixth position of the iron atom. The 3/3 Glbs of class 1 and the 2/2 Glbs (also called class 3 in plants) are present in all angiosperms, whereas the 3/3 Glbs of class 2 have been only found in early angiosperms and eudicots. The three Glb classes are expected to play different roles. Class 1 Glbs are involved in hypoxia responses and modulate NO concentration, which may explain their roles in plant morphogenesis, hormone signaling, cell fate determination, nutrient deficiency, nitrogen metabolism and plant–microorganism symbioses. Symbiotic Glbs derive from class 1 or class 2 Glbs and transport O₂ in nodules. The physiological roles of class 2 and class 3 Glbs are poorly defined but could involve O₂ and NO transport and/or metabolism, respectively. More research is warranted on these intriguing proteins to determine their non‐redundant functions.

中文翻译：

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植物血红蛋白：从单细胞绿藻到维管植物的旅程。

球蛋白（Glbs）广泛分布在古细菌，细菌和真核生物中。它们可以分为围绕血红素腔具有2/2或3/3α螺旋折叠的蛋白质。两种类型的Glbs都发生在绿藻，苔藓植物和维管植物中。对被子植物的Glbs进行了更深入的研究，并解决了几种蛋白质结构。它们可以是六配位或五配位的，这取决于组氨酸在铁原子的第六位是否配位。所有被子植物中均存在1类3/3 Glb和2/2 Glb（在植物中也称为3类），而2类3/3 Glb仅在早期被子植物和双子叶植物中发现。预计三个Glb类将扮演不同的角色。1类Glb参与缺氧反应并调节NO浓度，这可能解释了它们在植物形态发生，激素信号传导，细胞命运测定，营养缺乏，氮代谢和植物-微生物共生中的作用。共生Glbs源自1级或2级Glbs，转运O_2个结节。2类和3类Glbs的生理作用定义不清，但可能分别涉及O ₂和NO转运和/或新陈代谢。需要对这些有趣的蛋白质进行更多的研究，以确定它们的非冗余功能。