Stretched exponential decay and correlations in the catalytic activity of fluctuating single lipase molecules
Stretched exponential decay and correlations in the catalytic activity of fluctuating single lipase molecules
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DOI：
10.1073/pnas.0409039102
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发表时间：
2005-02-15
影响因子：
11.1
通讯作者：
Klafter, J
中科院分区：
文献类型：
--
作者：
Flomenbom, O;Velonia, K;Klafter, J
单分子技术为研究单个分子的动力学行为提供了独特的工具，并提供了从单个事件而不是从分子系综产生的信号构建分布的可能性。在以其复杂性而闻名的生物系统中，这些技术使人们有可能深入了解分子构象变化和活动的详细光谱。在这里，我们报告的直接观察一个单一的脂肪酶催化反应的时间延长（小时），通过使用共聚焦荧光显微镜。当添加促荧光底物时，监测的酶活性表现为“开状态”和“关状态”事件的轨迹。关态的等待时间概率密度函数和状态关联函数在一定范围内与底物浓度无关，均为拉伸指数函数。数据分析揭示了关闭状态等待时间概率密度函数的对数导数的振荡和关闭状态事件之间的相关性。这些研究结果意味着波动的酶模型，其中涉及的酶的构象，相互转换的催化活性的时间尺度上的频谱，最好的描述所观察到的酶的活性。基于该模型，提取耦合和反应速率的值。
Single-molecule techniques offer a unique tool for studying the dynamical behavior of individual molecules and provide the possibility to construct distributions from individual events rather than from a signal stemming from an ensemble of molecules. In biological systems, known for their complexity, these techniques make it possible to gain insights into the detailed spectrum of molecular conformational changes and activities. Here, we report on the direct observation of a single lipase-catalyzed reaction for extended periods of time (hours), by using confocal fluorescence microscopy. When adding a profluorescent substrate, the monitored enzymatic activity appears as a trajectory of "on-state" and "off-state" events. The waiting time probability density function of the off state and the state-correlation function fit stretched exponentials, independent of the substrate concentration in a certain range. The data analysis unravels oscillations in the logarithmic derivative of the off-state waiting time probability density function and correlations between off-state events. These findings imply that the fluctuating enzyme model, which involves a spectrum of enzymatic conformations that interconvert on the time scale of the catalytic activity, best describes the observed enzymatic activity. Based on this model, values for the coupling and reaction rates are extracted.