Protonation States of the Chromophore of Denatured Green Fluorescent Proteins Predicted by ab Initio Calculations

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• 作者：Jamal El Yazal ; Franklyn G. Prendergast ; David Elliot Shaw ; and Yuan-Ping Pang
• 刊名：Journal of the American Chemical Society
• 出版年：2000
• 出版时间：November 22, 2000
• 年：2000
• 卷：122
• 期：46
• 页码：11411 - 11415
• 全文大小：74K
• 年卷期：v.122,no.46(November 22, 2000)
• ISSN：1520-5126

文摘

Green fluorescent proteins (GFPs) are being intensively investigated due to both their unusual opticalspectroscopic characteristics and the extraordinary utility of GFPs as tools in biochemistry, cell biology, andmolecular genetics. Recent studies have suggested that the spectrophotometric and fluorescence characteristicsof GFPs are controlled through protonation states of the GFP chromophore (p-hydroxybenzylideneimidazolinone). However, of three protonation sites in the chromophore, only two have been studied. To understand thestructural origin of the observed spectrophotometric and fluorescence characteristics of GFPs, employing abinitio methods, we have investigated all the possible protonation sites of the chromophore of denatured GFPsunder different pH conditions. Our results suggest that the denatured GFP chromophore exists in not just twoprotonation states, as widely assumed in the literature, but in five different protonation states that depend onpH over the range -3.2 to 9.4 as assessed from the predicted pK_a values and the self-consistent reaction fieldcontinuum calculations of solvation employing Schrödinger's Jaguar 3.5 program. The unexpected complexityof the protonation states of the denatured GFP chromophore postulated here may provide a useful startingpoint for a further investigation of the protonation states of the intact GFP chromophore responsible for theexperimentally observed UV absorption and fluorescence emission properties of structurally intact GFPs.