期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 106, 期 26, 页码 10609-10613出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0904184106
关键词
CO2 binding; crystal pressurization; radiation driven reaction; substrate-product complex structure
资金
- European Commission (EC)
- CYTONET [HPRN-CT-2000-00096]
- EC 5th Framework Program Research and Technological Development Project EXMAD [HPRI-CT1999- 50015]
- EC 6th Framework Program Integrated Research project Biocrystallography
- BIOXHIT [LHSG-CT-2003-503420]
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.
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