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Crystal structure of a novel-type archaeal Rubisco with pentagonal symmetry

机译：五角对称的新型古细菌Rubisco的晶体结构

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Background: Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the key enzyme of the Calvin-Benson cycle and catalyzes the primary reaction of CO2 fixation in plants, algae, and bacteria. Rubiscos have been so far classified into two types. Type I is composed of eight large subunits (L subunits) and eight small subunits (S subunits) with tetragonal symmetry (L8S8), but type II is usually composed only of two L subunits (L-2). Recently, some genuinely active Rubiscos of unknown physiological function have been reported from archaea. Results: The crystal structure of Rubisco from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 (Tk-Rubisco) was determined at 2.8 a resolution. The enzyme is composed only of L subunits and showed a novel (L-2)(5) decameric structure. Compared to previously known type I enzymes, each L-2 dimer is inclined approximately 16 degrees to form a toroid-shaped decamer with its unique L-2-L-2 interfaces. Differential scanning calorimetry (DSC), circular dichroism (CD), and gel permeation chromatography (GPC) showed that Tk-Rubisco maintains its secondary structure and decameric assembly even at high temperatures. Conclusions: The present study provides the first structure of an archaeal Rubisco, an unprecedented (L-2)(5) decamer. Biochemical studies indicate that Tk-Rubisco maintains its decameric structure at high temperatures. The structure is distinct from type I and type II Rubiscos and strongly supports that Tk-Rubisco should be classified as a novel type III Rubisco. [References: 48]
机译：背景：核糖1,5-二磷酸羧化酶/加氧酶（Rubisco）是Calvin-Benson循环的关键酶，并催化植物，藻类和细菌中CO2固定的主要反应。迄今为止，Rubiscos已分为两种类型。 I型由八个大亚基（L个亚基）和八个小亚基（S个亚基）组成，具有四边形对称性（L8S8），但是II型通常仅由两个L个亚基（L-2）组成。最近，从古细菌中报道了一些生理功能未知的真正活性的Rubiscos。结果：来自超嗜热古细菌Thermococcus kodakaraensis KOD1（Tk-Rubisco）的Rubisco的晶体结构被确定为2.8分辨率。该酶仅由L个亚基组成，并显示出新颖的（L-2）（5）十聚结构。与以前已知的I型酶相比，每个L-2二聚体均倾斜约16度，以形成具有其独特L-2-L-2界面的环形十聚体。差示扫描量热法（DSC），圆二色性（CD）和凝胶渗透色谱法（GPC）表明，即使在高温下，Tk-Rubisco仍保持其二级结构和十聚体组装。结论：本研究提供了古细菌Rubisco的第一个结构，这是前所未有的（L-2）（5）弯角。生化研究表明，Tk-Rubisco在高温下可保持其十聚结构。该结构不同于I型和II型Rubisco，并强烈支持将Tk-Rubisco归类为新型III型Rubisco。 [参考：48]

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