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タイトル: | Formation of an unusually short hydrogen bond in photoactive yellow protein. |
著者: | Saito, Keisuke Ishikita, Hiroshi |
著者名の別形: | 石北, 央 |
キーワード: | Low-barrier hydrogen bond Proton transfer Photoactive yellow protein Laue diffraction crystallography [1]H NMR |
発行日: | 29-Nov-2012 |
誌名: | Biochimica et biophysica acta |
巻: | 1827 |
号: | 3 |
開始ページ: | 387 |
終了ページ: | 394 |
抄録: | The photoactive chromophore of photoactive yellow protein (PYP) is p-coumaric acid (pCA). In the ground state, the pCA chromophore exists as a phenolate anion, which is H-bonded by protonated Glu46 (O(Glu46)-O(pCA)=~2.6Å) and protonated Tyr42. On the other hand, the O(Glu46)-O(pCA) H-bond was unusually short (O(Glu46)-O(pCA)=2.47Å) in the intermediate pR(CW) state observed in time-resolved Laue diffraction studies. To understand how the existence of the unusually short H-bond is energetically possible, we analyzed the H-bond energetics adopting a quantum mechanical/molecular mechanical (QM/MM) approach based on the atomic coordinates of the PYP crystal structures. In QM/MM calculations, the O(Glu46)-O(pCA) bond is 2.60Å in the ground state, where Tyr42 donates an H-bond to pCA. In contrast, when the hydroxyl group of Tyr42 is flipped away from pCA, the H-bond was significantly shortened to 2.49Å in the ground state. The same H-bond pattern reproduced the unusually short H-bond in the pR(CW) structure (O(Glu46)-O(pCA)=2.49Å). Intriguingly, the potential-energy profile resembles that of a single-well H-bond, suggesting that the pK(a) values of the donor (Glu46) and acceptor (pCA) moieties are nearly equal. The present results indicate that the "equal pK(a)" requirement for formation of single-well or low-barrier H-bond (LBHB) is satisfied only when Tyr42 does not donate an H-bond to pCA, and argue against the possibility that the O(Glu46)-O(pCA) bond is an LBHB in the ground state, where Tyr42 donates an H-bond to pCA. |
著作権等: | © 2012 Elsevier B.V. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。 This is not the published version. Please cite only the published version. |
URI: | http://hdl.handle.net/2433/169709 |
DOI(出版社版): | 10.1016/j.bbabio.2012.11.009 |
PubMed ID: | 23201477 |
出現コレクション: | 学術雑誌掲載論文等 |
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