Department of Physics, Ohio State University, Columbus, OH 43210, USA.
Proc Natl Acad Sci U S A. 2010 Feb 16;107(7):2914-9. doi: 10.1073/pnas.1000001107. Epub 2010 Jan 26.
Dynamic solvation at binding and active sites is critical to protein recognition and enzyme catalysis. We report here the complete characterization of ultrafast solvation dynamics at the recognition site of photoantenna molecule and at the active site of cofactor/substrate in enzyme photolyase by examining femtosecond-resolved fluorescence dynamics and the entire emission spectra. With direct use of intrinsic antenna and cofactor chromophores, we observed the local environment relaxation on the time scales from a few picoseconds to nearly a nanosecond. Unlike conventional solvation where the Stokes shift is apparent, we observed obvious spectral shape changes with the minor, small, and large spectral shifts in three function sites. These emission profile changes directly reflect the modulation of chromophore's excited states by locally constrained protein and trapped-water collective motions. Such heterogeneous dynamics continuously tune local configurations to optimize photolyase's function through resonance energy transfer from the antenna to the cofactor for energy efficiency and then electron transfer between the cofactor and the substrate for repair of damaged DNA. Such unusual solvation and synergetic dynamics should be general in function sites of proteins.
动态溶剂化在蛋白质识别和酶催化中起着至关重要的作用。我们通过考察飞秒分辨荧光动力学和整个发射光谱，报告了在光天线分子的识别位点和酶光解酶辅因子/底物的活性位点超快溶剂化动力学的完整特征。通过直接使用内在天线和辅因子发色团，我们观察到了在几皮秒到近纳秒的时间尺度上的局部环境弛豫。与传统的溶剂化不同，在那里可以明显看到斯托克斯位移，我们在三个功能位点观察到明显的光谱形状变化，伴有较小、较小和较大的光谱位移。这些发射轮廓变化直接反映了发色团激发态受局部约束的蛋白质和被困水集体运动的调制。这种异质动力学通过从天线到辅因子的共振能量转移来连续调整局部构型，以提高光解酶的效率，然后在辅因子和底物之间进行电子转移，以修复受损的 DNA。这种不寻常的溶剂化和协同动力学在蛋白质的功能位点应该是普遍存在的。
