Structural study of X-ray induced activation of carbonic anhydrase
Structural study of X-ray induced activation of carbonic anhydrase
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DOI：
10.1073/pnas.0904184106
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发表时间：
2009-06-30
影响因子：
11.1
通讯作者：
Djinovic-Carugo, Kristina
中科院分区：
文献类型：
--
作者：
Sjoeblom, Bjoern;Polentarutti, Maurizio;Djinovic-Carugo, Kristina
碳酸酐酶是一种锌金属酶，催化二氧化碳可逆水合为碳酸氢盐。它参与与酸碱平衡、呼吸和光合作用有关的过程。在过去的30年中，已经产生了超过100种不同的人碳酸酐酶II（HCAII）3D结构[Liljas A，et al.（1972）Nat New Biol 235：131-137]，但是与CO2或HCO 3-复合的HCAII的结构仍然难以捉摸。在这里，我们报告以前未描述的HCAII：CO2和HCAII：HCO 3-复合物的结构，连同连续观察到的酶促反应的3D分子膜在同一晶体后，延长暴露于X射线。我们证明，意想不到的酶激活引起的X射线剂量依赖性的方式。尽管X射线对大分子样品的损伤早已被认识[Ravelli RB，Garman EF（2006）Curr Opin Struct Biol 16：624-629]，但迄今为止，关于X射线驱动反应的详细结构分析报告在文献中非常罕见。在这里，我们报告在100 K的晶体中的酶激活和相关的化学反应。我们提出了基于水的光辐射分解和/或电子辐射分解的机制作为酶激活的主要原因。
Carbonic anhydrase, a zinc metalloenzyme, catalyzes the reversible hydration of carbon dioxide to bicarbonate. It is involved in processes connected with acid-base homeostasis, respiration, and photosynthesis. More than 100 distinct human carbonic anhydrase II (HCAII) 3D structures have been generated in last 3 decades [Liljas A, et al. (1972) Nat New Biol 235: 131-137], but a structure of an HCAII in complex with CO2 or HCO3- has remained elusive. Here, we report previously undescribed structures of HCAII: CO2 and HCAII: HCO3- complexes, together with a 3D molecular film of the enzymatic reaction observed successively in the same crystal after extended exposure to X-ray. We demonstrate that the unexpected enzyme activation was caused in an X-ray dose-dependent manner. Although X-ray damage to macromolecular samples has long been recognized [Ravelli RB, Garman EF (2006) Curr Opin Struct Biol 16: 624-629], the detailed structural analysis reports on X-ray-driven reactions have been very rare in literature to date. Here, we report on enzyme activation and the associated chemical reaction in a crystal at 100 K. We propose mechanisms based on water photoradiolysis and/or electron radiolysis as the main cause of enzyme activation.